Appeal to provide the head of police with a clue (5)
I believe the answer is:
plead
'appeal to' is the definition.
(thesaurus)
'the head of police with a clue' is the wordplay.
'the head of' indicates taking the first letters.
'with' means one lot of letters go next to another.
'a clue' becomes 'lead' (e.g. in a police investigation).
The initial letter of 'police' is 'p'.
'p'+'lead'='PLEAD'
'provide' is the link.
(Other definitions for plead that I've seen before include "Argue (a position in court)" , "Supplicate" , "State whether one is guilty or not" , "Appeal humbly (to)" , "Present an argument in court" .)