Agree with head office quarry's been identified (5-2)
I believe the answer is:
tally-ho
'quarry's been identified' is the definition.
(hunting cry given when prey or quarry is found)
'agree with head office' is the wordplay.
'agree' becomes 'tally' (synonyms).
'with' says to put letters next to each other.
'head office' becomes 'ho'.
'tally'+'ho'='TALLY-HO'
(Other definitions for tally-ho that I've seen before include "Hunt cry" , ""I've seen the fox!"" , "Cry of the huntsman pursuing the fox" , "Fox-hunting cry" , "Hunter's cry" .)