Tolerate final treatment after head’s cut (6)
I believe the answer is:
endure
'tolerate' is the definition.
(I know that tolerate can be written as endure)
'final treatment after head's cut' is the wordplay.
'final' becomes 'end' (synonyms).
'treatment' becomes 'cure' (medical treatment).
'after head's cut' means to remove the first letter.
'cure' with its initial letter taken away is 'ure'.
'end'+'ure'='ENDURE'
(Other definitions for endure that I've seen before include "Stomach" , "brook" , "Put up with something" , "Go through" , "'Last, bear (6)'" .)