Rev might, after inviting duke in for tea (9)
I believe the answer is:
gunpowder
'for tea' is the definition.
(I've seen this before)
'rev might after inviting duke' is the wordplay.
'rev' becomes 'gun' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'might' becomes 'power' (synonyms).
'after' is a charade indicator (letters next to each other).
'inviting' is an insertion indicator.
'duke' becomes 'd'.
'gun'+'power'='gunpower'
'gunpower' going around 'd' is 'GUNPOWDER'.
'in' is the link.
Can you help me to learn more?
(Other definitions for gunpowder that I've seen before include "It's used in gunnery and fireworks" , "likely to go up?" , "and 24: 1605 conspiracy" , "Ingredient of fireworks" , "Explosive; type of 23 dn" .)