Policeman joining bishop - very good (6)
I believe the answer is:
superb
'good' is the definition.
(thesaurus)
'policeman joining bishop' is the wordplay.
'policeman' becomes 'super' (short for superintendant).
'joining' says to put letters next to each other.
'bishop' becomes 'B' (chess abbreviation).
'super'+'b'='SUPERB'
'very' is the link.
(Other definitions for superb that I've seen before include "'Excellent, brilliant (6)'" , "First-class" , "Dazzling" , "Dusty product of spider" , "Gorgeous" .)