Amount of hair (4)
I believe the answer is:
hank
'amount of hair' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hank that I've seen before include "-- Marvin, guitarist" , "Loop of cord" , "Coil of wool for American Henry" , "Skein (of wool, etc)" , "Henry - coil of rope, wool or yarn" .)