Learnt about regular payment (6)
I believe the answer is:
rental
'regular payment' is the definition.
(rent payments)
'learnt about' is the wordplay.
'about' is an anagram indicator.
'learnt' is an anagram of 'RENTAL'.
(Other definitions for rental that I've seen before include "money for landlord" , "Charge to hirer" , "Payment for hire" , "To do with a letting" , "Hire charge" .)