Round of applause given to fish expert (3,4)
I believe the answer is:
dab hand
'expert' is the definition.
(I've seen this before)
'round of applause given to fish' is the wordplay.
'round of applause' becomes 'hand' (I've seen this before).
'given to' is a charade indicator (letters next to each other).
'fish' becomes 'dab' (I've seen this before).
'hand' after 'dab' is 'DAB HAND'.
(Other definitions for dab hand that I've seen before include "An informal expert such as band had" , "cursory wash?" , "Past master" , "Barely wash" .)