English soldier gets millions in fiddle (5)
I believe the answer is:
tommy
'english soldier' is the definition.
(informal term for an English soldier)
'millions in fiddle' is the wordplay.
'millions' becomes 'mm' (m is an abbreviation for million).
'in' means one lot of letters goes inside another.
'fiddle' becomes 'toy' (synonyms).
'mm' going within 'toy' is 'TOMMY'.
'gets' is the link.
(Other definitions for tommy that I've seen before include "Doubtful apostle could be so familiar" , "Private soldier (slang)" , "Bread" , "British soldier (informal)" , "British private soldier (colloq.)" .)