Monk's wool supplier losing head (4)
I believe the answer is:
lama
'monk's' is the definition.
(I've seen this before)
'wool supplier losing head' is the wordplay.
'wool supplier' becomes 'llama' (I've seen this before).
'losing head' means to remove the first letter.
'llama' with its initial letter taken away is 'LAMA'.
(Other definitions for lama that I've seen before include "Religious leader" , "A Buddist monk in Tibet" , "Tibetan spiritual leader" , "devout Buddhist" , "Holy man in Tibet" .)