It's more difficult when miser gives nothing away (6)
I believe the answer is:
harder
'it's more difficult' is the definition.
('hard' can be a synonym of 'difficult')
'miser gives nothing away' is the wordplay.
I cannot quite see how this works, but
'away' could be 'ard' (I've seen this in other clues) and 'ard' is found within the answer.
The remaining letters 'her' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'when' is the link.
Can you help me to learn more?
(Other definitions for harder that I've seen before include "More tough or difficult" , "More solid" .)