Buckle after fighting pressure (4)
I believe the answer is:
warp
'buckle' is the definition.
(synonyms)
'after fighting pressure' is the wordplay.
'after' says to put letters next to each other.
'fighting' becomes 'war'.
'pressure' becomes 'p' (abbreviation).
'war' put next to 'p' is 'WARP'.
(Other definitions for warp that I've seen before include "Pervert - distort" , "Make bent or twisted" , "Twist out of shape" , "Abnormality in character" , "Misintepret" .)