Rebuke salesperson given fish (8)
I believe the answer is:
Here is my best explanation:
'rebuke' is the definition.
(reproach is a kind of rebuke)
'salesperson given fish' is the wordplay.
'salesperson' becomes 'rep' (I've seen this before).
'given' says to put letters next to each other.
'fish' becomes 'roach' (roach is a kind of fish**).
(Other definitions for reproach that I've seen before include "criticise", "Blame, scold", "Berate", "Castigate", "Take to task", "Express disapproval to (someone)", "Scold(ing)", "approval? Just the opposite", "Chide" and "Expression of disapproval".)