Wimp in conflict interrupting swimmer (6)
I believe the answer is:
coward
'wimp' is the definition.
(I've seen this before)
'conflict interrupting swimmer' is the wordplay.
'conflict' becomes 'war' (war is a kind of conflict).
'interrupting' indicates putting letters inside.
'swimmer' becomes 'cod' (type of fish).
'war' put within 'cod' is 'COWARD'.
'in' is the link.
(Other definitions for coward that I've seen before include "Person lacking courage" , "Yellow-belly" , "who would shy away from difficulties?" , "whose encounter was briefly filmed" , "Scaredy-cat" .)