Judge is on fire, lacking passion (3)
I believe the answer is:
ref
'judge' is the definition.
'on fire lacking passion' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to'**).
'lacking' suggests deleting specific letters.
'passion' becomes 'ire' (I've seen this before).
'fire' with 'ire' taken away is 'f'.
're'+'f'='REF'
'is' is the link.
(Other definitions for ref that I've seen before include "A diminutive umpire in soccer or boxing" , "'Game judge, in short (3)'" , "Sports umpire" , "Whistleblower (abbr)" , "Football's whistler" .)