Earn millions before tax returns (5)
I believe the answer is:
merit
'earn' is the definition.
(I've seen this before)
'millions before tax returns' is the wordplay.
'millions' becomes 'm' (abbreviation).
'before' means one lot of letters go next to another.
'tax' becomes 'tire' (I've seen this in another clue).
'returns' says the letters should be written in reverse.
'tire' reversed gives 'erit'.
'm'+'erit'='MERIT'
(Other definitions for merit that I've seen before include "Good point or quality" , "Just deserts" , "Deserve; excellence" , "Excellence, desert" , "The M in OM" .)