Fine! I will tuck into fishy food for a starter (6)
I believe the answer is:
rookie
'for a starter' is the definition.
'fine i will tuck into fishy food' is the wordplay.
'fine' becomes 'ok' (synonyms).
'will tuck into' indicates putting letters inside.
'fishy food' becomes 'roe' (roe is a kind of food. I am not sure about the 'fishy' bit.).
'ok'+'i'='oki'
'oki' put into 'roe' is 'ROOKIE'.
Can you help me to learn more?
(Other definitions for rookie that I've seen before include "Novice" , "untested type" , "Raw recruit" , "new team member" , "Callow recruit" .)