Having lost bottle, he blew unfairly (5,3,4)
I believe the answer is:
below the belt
'unfairly' is the definition.
(below the belt means unfair)
'having lost bottle he blew' is the wordplay.
'having lost' indicates anagramming the letters (the original order is lost).
'bottle'+'he'+'blew'='bottleheblew'
'bottleheblew' is an anagram of 'BELOW THE BELT'.
(Other definitions for below the belt that I've seen before include "out of order" , "Unsporting" , "Hang scabbard here" , "Underhand, unfair" , "fly is here" .)