The most common and most likely answer to this crossword clue is the 18 letter word HONEST-TO-GOODNESS
I've seen this crossword clue in The Times
H
O
N
E
S
T
-
T
O
-
G
O
O
D
N
E
S
S
Buddy explains!

The straight part
We know that "Well, really" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case well, really = honest-to-goodness.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 HONEST-TO-GOODNESS mean?
HONEST-TO-GOODNESS adverb- Honest; truly, really; used to emphasize that a statement is true.
- (attributive only) Real; genuine.