Lean son overlooking bank, perhaps (7)
I believe the answer is:
slender
'lean son' is the definition.
'slender' can be an answer for 'lean' (I've seen this before). I'm not certain of the 'son' bit.
'overlooking bank perhaps' is the wordplay.
'overlooking' is a charade indicator (letters next to each other) (in a down clue, some letters go above others).
'bank' becomes 'lender'.
'perhaps' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'lender' put after 's' is 'SLENDER'.
Can you help me to learn more?
(Other definitions for slender that I've seen before include "Spare" , "short of a pound or two of flesh?" , "Willowy" , "Slight, slim" , "Fine" .)