Good to discover the truth about beef (7)
I believe the answer is:
grumble
'beef' is the definition.
(thesaurus)
'good to discover the truth' is the wordplay.
'good' becomes 'g' (abbreviation).
'to discover the truth' becomes 'rumble'.
'g'+'rumble'='GRUMBLE'
'about' acts as a link.
(Other definitions for grumble that I've seen before include "Moan" , "bitch" , "Complain, protest" , "Murmur with discontent" , "Complain, be a grouch" .)