Learnt about payment (6)
I believe the answer is:
rental
'payment' is the definition.
(I've seen this before)
'learnt about' is the wordplay.
'about' indicates anagramming the letters.
'learnt' is an anagram of 'RENTAL'.
(Other definitions for rental that I've seen before include "money for landlord" , "Hire fee" , "Cost of hire" , "Payment for use -- antler (anag)" , "Amount paid for hire" .)