Cornish banker in decline spared last pound (3)
I believe the answer is:
fal
'cornish banker' is the definition.
(River Fal in Cornwall, something which 'banks')
'decline spared last pound' is the wordplay.
I cannot really understand how this works, but
'last' could be 'f' (I've seen this in other clues) and 'f' is located in the answer.
'pound' could be 'l' (abbreviation e.g. Lsd - pounds, shillings, pence) and 'l' is located in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for fal that I've seen before include "Flower" , "Cornish river" .)