Insignificant, fifteen cents in the US? (6,3,4)
I believe the answer is:
nickel-and-dime
'insignificant fifteen' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?
'cents in the us?' is the wordplay.
I cannot quite understand how this works, but
'cents' could be 'dime' (ten cent US coin) and 'dime' is found in the answer.
'us?' could be 'land' (us is a kind of land) and 'land' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for nickel-and-dime that I've seen is " Trivial (US)".)