A shock for the head! (3)
I believe the answer is:
mop
I believe this clue is a double definition.
'a shock' is the first definition.
(thesaurus)
'the head' is the second definition.
(I have seen 'head of hair' mean 'mop' so perhaps 'head' could also mean 'mop')
'for' acts as a link.
(Other definitions for mop that I've seen before include "Bundle of soft material at end of stick for cleaning" , "Shock of hair; soak (up)" , "Swab" , "Cleaning implement" , "Hair, unkempt" .)