Fisherman’s aid (3)
I believe the answer is:
net
'fisherman's aid' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for net that I've seen before include "Catch, ensnare" , "Clear profit or gain" , "Fish trap and type of goal" , "Open weave fabric" , "device to divide the court" .)