Those offering unwanted advice to endorse chair for motorists (8,7)

I believe the answer is:

backseat drivers

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'those offering unwanted advice' is the definition.
I can't tell whether this defines the answer.

'endorse chair for motorists' is the wordplay.
'endorse' becomes 'back' (synonyms).
'chair' becomes 'seat' (something to sit on).
'for' is a charade indicator (letters next to each other).
'motorists' becomes 'drivers' (I've seen this before).
'back'+'seat'+'drivers'='BACKSEAT DRIVERS'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for backseat drivers that I've seen before include "irresponsible advisors" , "self-opinionated travellers" .)

I've seen this clue in The Irish Times.

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