Hermit - a person having doubts spending penny (7)
I believe the answer is:
ascetic
'hermit' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for ascetic that I've seen before include "Severely disciplined" , "Self-denier" , "Austere, abstinent" , "Austere type" , "Self-denying, not allowing oneself luxuries" .)