There's purpose in regular payment for clothes (7)
I believe the answer is:
raiment
'clothes' is the definition.
(raiment is a kind of clothes)
'there's purpose in regular payment' is the wordplay.
'there's purpose' becomes 'aim' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'regular payment' becomes 'rent' (rent is a kind of regular payment).
'aim' put inside 'rent' is 'RAIMENT'.
'for' is the link.
Can you help me to learn more?
(Other definitions for raiment that I've seen before include "Old word for fine clothing" , "Clobber" , "Wear" , "Apparel" , "Poetic word for clothing" .)