Skewer bananas upside down (4)
I believe the answer is:
stab
'skewer' is the definition.
(I've seen this in another clue)
'bananas upside down' is the wordplay.
'bananas' becomes 'bats' (I've seen this before).
'upside down' is a reversal indicator.
'bats' backwards is 'STAB'.
(Other definitions for stab that I've seen before include "pink" , "Strike with knife" , "Pierce with pointed weapon" , "effort" , "Jab" .)