Hobby in father's era (7)
I believe the answer is:
pastime
'hobby' is the definition.
(I've seen this before)
'father's era' is the wordplay.
'father's' becomes 'pa's' (pa can mean dad or father).
'era' becomes 'time' (I've seen this in another clue).
'pas'+'time'='PASTIME'
'in' acts as a link.
(Other definitions for pastime that I've seen before include "Leisure activity" , "diversion" , "relaxation" , "Leisure pursuit" , "Hobby; regular activity" .)