Piercing whistle — ref's blowing up too much (7)
I believe the answer is:
surfeit
'too much' is the definition.
'piercing whistle ref's blowing up' is the wordplay.
'piercing' is an insertion indicator (some letters pierce a hole in others).
'whistle' becomes 'suit' (whistle and flute is rhyming slang for a suit).
'blowing up' is an anagram indicator.
'ref' with letters rearranged gives 'rfe'.
'suit' enclosing 'rfe' is 'SURFEIT'.
(Other definitions for surfeit that I've seen before include "it's more than one needs" , "excessive amount" , "Fustier (anag)" , "Overindulge" , "Superabundance" .)