Convince it's fantasy (4,7)
I believe the answer is:
make believe
I believe this is a double definition.
'convince' is the first definition.
(I've seen this before)
'fantasy' is the second definition.
(I've seen this before)
'it's' is the link.
(Other definitions for make believe that I've seen before include "Sham" , "Fancy" , "Pretend" , "Pretence" , "Convince - fantasise" .)