Do well: ten caught among fish (5)
I believe the answer is:
excel
'do well' is the definition.
(I've seen this before)
'ten caught among fish' is the wordplay.
'ten' becomes 'X' (Roman numeral).
'caught' becomes 'c' (cricket abbreviation).
'among' means one lot of letters goes inside another (inserted letters are placed among others).
'fish' becomes 'eel' (eel is a type of fish).
'x'+'c'='xc'
'xc' inserted inside 'eel' is 'EXCEL'.
(Other definitions for excel that I've seen before include "cap" , "Be superior to" , "Perform exceptionally well" , "Every one" , "Perform outstandingly well" .)