Cabbies really don't need their tips (8,7)
I believe the answer is:
backseat drivers
'cabbies' is the definition.
The definition and answer can be both people as well as being plural nouns.
Maybe they are linked in a way I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for backseat drivers that I've seen before include "self-opinionated travellers" , "irresponsible advisors" .)