What mechanic recommends makes relative stop dead, reportedly (10)
I believe the answer is:
antifreeze
'what mechanic recommends makes relative' is the definition.
I can't judge whether this defines the answer.
'stop dead reportedly' is the wordplay.
I cannot quite see how this works, but
'stop' could be 'freeze' (I've seen this before) and 'freeze' is found in the answer.
The remaining letters 'anti' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for antifreeze that I've seen before include "which prevents ice damage" , "Addition to radiator" , "Winter essential in engines" , "Winter radiator additive" , "It keeps thing flowing" .)