One’s little more than extra restraint: pound retained by one making expenditure (3,6)
I believe the answer is:
bit player
'one's little more' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'extra restraint pound retained by one making expenditure' is the wordplay.
I cannot quite see how this works, but
'extra' could be 'b' (abbreviation for 'bye' - cricket) and 'b' is found within the answer.
'pound' could be 'l' (the pound sign is based on an L) and 'l' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'expenditure' could be 'pay' (pay is a kind of expenditure) and 'pay' is located in the remaining letters.
The remaining letters 'ter' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'than' is the link.
Can you help me to learn more?
(Other definitions for bit player that I've seen before include "minor party" , "Actor with minor part" , "extra" .)