The most common and most likely answer to this crossword clue is the 12 letter word ATTITUDINISE
I've seen this crossword clue in Independent
A
T
T
I
T
U
D
I
N
I
S
E
More clues leading to the result ATTITUDINISE
Buddy explains!
The straight part
We know that "to adopt a pose for effect" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to adopt a pose for effect = attitudinise.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 ATTITUDINISE mean?
ATTITUDINISE verb- To assume an affected, unnatural exaggerated attitude or pose.
- To cause to assume a pose.
- To give the appearance of, make a show of by posing.