Snappy taxi driver tucks right in (6)
I believe the answer is:
crabby
'snappy' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'taxi driver tucks right in' is the wordplay.
'taxi driver' becomes 'cabby' (I've seen this before).
'tucks right' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'cabby' enclosing 'r' is 'CRABBY'.
Can you help me to learn more?
(Other definitions for crabby that I've seen before include "like a hermit?" , "In bad temper" , "Ill-natured" , "Irritable - like a crustacean?" , "Temperamental" .)