Get to grips with hair round growth on head (4,5)
I believe the answer is:
lock horns
'get to grips with' is the definition.
(both can mean to engage in conflict)
'hair round growth on head' is the wordplay.
'hair' becomes 'locks' (I've seen this before).
'round' is an insertion indicator.
'growth on head' becomes 'horn'.
'locks' going around 'horn' is 'LOCK HORNS'.
(Other definitions for lock horns that I've seen before include "Engage in combat" , "Fight" , "Start to do battle" , "join battle" , "Engage in struggle" .)