The most common and most likely answer to this crossword clue is the 8 letter word EXTERNAL
I've seen this crossword clue in Independent
E
X
T
E
R
N
A
L
More clues leading to the result EXTERNAL
- Outward-looking, not stopping to accept mark of censure
- Old bird and bloke outside
- Going on for ever about unidentified person outside
- Cross endless borders from elsewhere
- Outside bird caged by old metal
- Old seabird’s regularly able to get outside
- Enduring restricted times for lying outside
- Everlasting cross goes inside and outside
- Superficial, relentless, securing vote
- Superficial old bird, vacuously amoral
Buddy explains!

The straight part
We know that "lying outside" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lying outside = external.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 EXTERNAL mean?
EXTERNAL noun- (chiefly in the plural) The exterior; outward features or appearances.
- In the C programming language, a variable that is defined in the source code but whose value comes from some external source.
- Outside of something; on the exterior.
- Not intrinsic nor essential; accidental; accompanying; superficial.
- Foreign; relating to or connected with foreign nations.
- Away from the mesial plane of the body; lateral.
- Provided by something or someone outside of the entity (object, group, company etc.) considered.