Cocktail has oomph with vermouth added in (6)

I believe the answer is:
mojito
'cocktail' is the definition.
(rum-based cocktail)
'oomph with vermouth added in' is the wordplay.
I cannot really see how this works, but
'oomph' could be 'it' (both can mean a special or striking quality) and 'it' is located in the answer.
The remaining letters 'mojo' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'has' is the link.
Can you help me to learn more?
(Other definitions for mojito that I've seen before include "Cuban cocktail with rum as a base" , "Minty cocktail" , "Cuban rum-and-lime-based cocktail" , "Mexican cocktail made with white rum and lime juice" , "'Cuban cocktail made from rum, lime etc (6)'" .)
