The most common and most likely answer to this crossword clue is the 8 letter word ABSOLUTE
I've seen this crossword clue in The Guardian
A
B
S
O
L
U
T
E
More clues leading to the result ABSOLUTE
- Rank or ratings associated with old music maker
- Peremptory solicitor probing a nobbler’s drug
- Rank ratings given by old music-maker
- Complete louts on the rampage in Lincoln
- Inside wash: very pure
- Pure tar’s a dissolved substance
- Total absence leads to old lover undergoing tearful emotions
- Bale’s out injured for certain
- Certain muscles shown by ill- disciplined lout close to home
- Certain instrument on which sailors introduce Offenbach
Buddy explains!

The straight part
We know that "Complete" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case complete = absolute.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ABSOLUTE mean?
ABSOLUTE noun- That which is independent of context-dependent interpretation, inviolate, fundamental.
- Anything that is absolute.
- In a plane, the two imaginary circular points at infinity; in space of three dimensions, the imaginary circle at infinity.
- (usually capitalized) A realm which exists without reference to anything else; that which can be imagined purely by itself; absolute ego.
- (usually capitalized) The unity of spirit and nature; God.
- (usually capitalized) The whole of reality; the totality to which everything is reduced.
- A concentrated natural flower oil, used for perfumes; an alcoholic extract of a concrete.
- Free of restrictions, limitations, qualifications or conditions; unconditional.
- Free from imperfection, perfect, complete; especially, perfectly embodying a quality in its essential characteristics or to its highest degree.
- Pure, free from mixture or adulteration; unmixed.
- Complete, utter, outright; unmitigated, not qualified or diminished in any way.
- Positive, certain; unquestionable.
- Certain; free from doubt or uncertainty (e.g. a person, opinion or prediction).
- Fundamental, ultimate, intrinsic; not relative; independent of references or relations to other things or standards.
- Independent of arbitrary units of measurement, standards, or properties; not comparative or relative.
- (grammar) Not immediately dependent on the other parts of the sentence; not in a syntactical relation with other parts of a text, or qualifying the text as a whole rather than any single word in it, like "it being over" in "it being over, she left".
- As measured using an absolute value.
- Indicating an expression that is true for all real numbers, or of all values of the variable; unconditional.
- Pertaining to a grading system based on the knowledge of the individual and not on the comparative knowledge of the group of students.
- Independent of (references to) other arts; expressing things (beauty, ideas, etc) only in one art.
- Absolved; free.