Reportedly ruined fishes' shapes (10)
I believe the answer is:
rectangles
'shapes' is the definition.
(rectangle is a kind of shape)
'reportedly ruined fishes'' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'ruined' becomes 'wrecked' (to wreck something is to ruin or spoil it).
'fishes'' becomes 'angles' ('angle' can be a synonym of 'fish').
'wrecked' is a homophone of 'rect'.
'rect'+'angles'='RECTANGLES'
(Other definitions for rectangles that I've seen before include "Four-sided figures" , "they may be squares" .)