Light blows are what fishermen require (6)
I believe the answer is:
smacks
'light blows' is the definition.
'smacks' can be an answer for 'blows' (smack is a kind of blow). I am not certain of the 'light' bit.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for smacks that I've seen before include "Has a hint (of)" , "Punishes" , "Boxes" , "Slaps the fishing boats?" , "Hits the fishing vessels" .)