Polish line in elevated bank (5)
I believe the answer is:
bluff
'elevated bank' is the definition.
'bluff' can be an answer for 'bank' (bluff is a kind of bank). I'm not certain of the 'elevated' bit.
'polish line in' is the wordplay.
'polish' becomes 'buff' (buffing is a kind of polishing).
'line' becomes 'l' (used when specifying particular lines from a poem).
'in' means one lot of letters goes inside another.
'buff' enclosing 'l' is 'BLUFF'.
Can you help me to learn more?
(Other definitions for bluff that I've seen before include "Frank, direct; steep cliff" , "What a poker player does - or tries to" , "Hoodwink" , "Deception - hearty" , "Challengers may call it" .)