Tart in live performance initially reversing vehicle (7)
I believe the answer is:
pedicab
'vehicle' is the definition.
(pedicab is a kind of vehicle)
'tart in live performance initially reversing' is the wordplay.
'tart' becomes 'acid' (I've seen this before).
'in' means one lot of letters goes inside another.
'live' becomes 'be' ('be' can be a synonym of 'live').
'performance initially' becomes 'p' (I can't justify this - if you can you should believe this answer much more).
'reversing' shows that the letters should be reversed in order.
'be'+'p'='bep'
'acid' placed inside 'bep' is 'bacidep'.
'bacidep' backwards is 'PEDICAB'.
Can you help me to learn more?
(Other definitions for pedicab that I've seen before include "Tricycle with hooded seat at rear" , "Man-powered taxi" , "tricycle for hire" , "with which one might be taken for a ride" , "Hire-vehicle" .)