Farrow back in goal (3)
I believe the answer is:
aim
'goal' is the definition.
(aim is a kind of goal)
'farrow back' is the wordplay.
'farrow' becomes 'mia' (I've seen this in another clue).
'back' shows that the letters should be reversed in order.
'mia' back-to-front is 'AIM'.
'in' acts as a link.
(Other definitions for aim that I've seen before include "Set sights on, target or goal" , "Set sights on, say target" , "Plan" , "Steady, ... fire" , "Draw a bead on" .)