Typical farmer astride gee-gee is a funny fit! (7)
I believe the answer is:
giggles
'a funny fit' is the definition.
(as in a fit of giggles)
'typical farmer astride gee-gee' is the wordplay.
'typical farmer' becomes 'Giles' (Farmer Giles is a stereotypical name for a farmer).
'astride' indicates putting letters inside.
'gee' becomes 'g' (synonyms).
'gee' becomes 'g' (synonyms).
'g'+'g'='gg'
'giles' placed around 'gg' is 'GIGGLES'.
'is' is the link.
(Other definitions for giggles that I've seen before include "Has a chuckle" , "Uncontrollable laughter" , "Titters" , "Nervous laughs" .)