Go with bank's first loan (5)
I believe the answer is:
blend
'go' is the definition.
(synonyms)
'with bank's first loan' is the wordplay.
'with' means one lot of letters go next to another.
'bank's first' becomes 'b' (1st letter of 'bank').
'loan' becomes 'lend' (synonyms).
'b'+'lend' is 'BLEND'.
(Other definitions for blend that I've seen before include "Mix together" , "Coalesce" , "Mingle" , "Fusion" , "Combine together" .)