Mean to accept old fine? Certainly not (2,4)
I believe the answer is:
no fear
'certainly not' is the definition.
(phrase used to express a denial or refusal)
'mean to accept old fine?' is the wordplay.
'mean' becomes 'near' (both can mean miserly).
'to accept' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'fine?' becomes 'f' (abbreviation).
'o'+'f'='of'
'near' going around 'of' is 'NO FEAR'.
(Other definitions for no fear that I've seen before include "Not on your life, certainly not" , "Never" , "Informally, certainly not., who's afraid" , "what the bold show" , "Far one (anag.)" .)