Interest charged one pound at a time (5)
I believe the answer is:
april
'time' is the definition.
(I've seen this before)
'interest charged one pound at a' is the wordplay.
'interest charged one' becomes 'pri' (I can't justify this - if you can you should give a lot more credence to this answer).
'pound' becomes 'L' (abbreviation e.g. Lsd - pounds, shillings, pence).
'at' means one lot of letters go next to another (I've seen this in other clues).
'pri'+'l'='pril'
'pril' put after 'a' is 'APRIL'.
Can you help me to learn more?
(Other definitions for april that I've seen before include "Start of the financial year" , "Month that's autumnal in Oz" , "time of the year" , "Month to be in England (Browning)" , "First month of the year with 30 days" .)