Fruit fly, back near fiancé every so often (9)
I believe the answer is:
tangerine
'fruit' is the definition.
(tangerine is a kind of fruit)
'fly back near fiance every so often' is the wordplay.
'fly' becomes 'gnat' (type of insect).
'back' is a reversal indicator.
'every so often' indicates alternate letters.
'near'+'fiance'='nearfiance'
The alternate letters of 'nearfiance' are 'erine'.
'gnat' backwards is 'tang'.
'tang'+'erine'='TANGERINE'
(Other definitions for tangerine that I've seen before include "Variety of mandarin orange" , "Small citrus fruit with a loose skin" , "fruit product" , "Green tan I change into orange" , "Taste" .)