Like large piece? Fish is excellent (5,4)
I believe the answer is:
hunky dory
'excellent' is the definition.
(I've seen this before)
'like large piece? fish' is the wordplay.
'like large piece?' becomes 'hunky' (hunk can mean a large piece of something).
'fish' becomes 'dory' (dory is a kind of fish).
'hunky'+'dory'='HUNKY-DORY'
'is' is the link.
(Other definitions for hunky dory that I've seen before include "excellent" , "Great" , "From America, fine" , "album" , "Splendid" .)