Fresh head on stick (6)
I believe the answer is:
adhere
'stick' is the definition.
(to adhere to something is to stick to it)
'fresh head on' is the wordplay.
'fresh' is an anagram indicator (a fresh re-ordering of the letters).
'on' becomes 're' ('on' can be mean 'with reference to').
'head' with letters rearranged gives 'adhe'.
'adhe'+'re'='ADHERE'
(Other definitions for adhere that I've seen before include "Stick to or remain faithful" , "Stick to as by suction" , "paste" , "Stick to, cling" , "Agree" .)