Western banker always invested in tin (6)
I believe the answer is:
severn
'western banker' is the definition.
'severn' can be an answer for 'banker' (I have seen 'British banker' mean 'severn' so perhaps 'banker' could also mean 'severn'). I am not sure about the 'western' bit.
'always invested in tin' is the wordplay.
'always' becomes 'ever' (synonyms).
'invested in' means one lot of letters goes inside another.
'tin' becomes 'Sn' (Sn is the chemical symbol for tin).
'ever' put within 'sn' is 'SEVERN'.
Can you help me to learn more?
(Other definitions for severn that I've seen before include "GB's longest river" , "River at Gloucester" , "Longest British river" , "Flower" , "River at Worcester" .)