Seafood right inside taxi (4)
I believe the answer is:
crab
'seafood' is the definition.
(crab is a kind of seafood)
'right inside taxi' is the wordplay.
'right' becomes 'r' (common abbreviation).
'inside' indicates putting letters inside.
'taxi' becomes 'cab' (synonyms).
'r' inserted inside 'cab' is 'CRAB'.
(Other definitions for crab that I've seen before include "One may be caught" , "one is a fiddler" , "Ten-legged shellfish" , "Clawed crustacean" , "Nautical nipper" .)