Growing up, miss your old man? (7)
I believe the answer is:
timothy
'man?' is the definition.
'growing up miss your old' is the wordplay.
'growing up' says the letters should be written backwards.
'miss' becomes 'omit' (synonyms).
'your old' becomes 'thy' ('thy' historically meant 'your').
'omit' back-to-front is 'timo'.
'timo'+'thy'='TIMOTHY'
(Other definitions for timothy that I've seen before include "Biblical writer" , "Bible book" , "A grass; an NT disciple" , "New Testament book" , "Grass; boy's name" .)