Self-denying (7)
I believe the answer is:
ascetic
'self-denying' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for ascetic that I've seen before include "Severely self-disciplined" , "Practising severe self-discipline" , "One avoiding indulgence" , "Religiously self-disciplined" , "One practising self-denial as a discipline" .)