Person with bad manners and humour brought to head to give evidence (4,7)
I believe the answer is:
bear witness
'give evidence' is the definition.
(thesaurus)
'person with bad manners and humour brought to head' is the wordplay.
'person with bad manners' becomes 'bear' (bear can mean a rude person).
'and' is a charade indicator (letters next to each other).
'humour' becomes 'wit' (synonyms).
'brought to' means one lot of letters go next to another.
'head' becomes 'ness' (ness is a headland).
'bear'+'wit'+'ness'='BEAR WITNESS'
'to' is the link.
(Other definitions for bear witness that I've seen before include "Testify (to)" , "Give testimony" .)