Car repairs botched with loss of power (6)
I believe the answer is:
sierra
'loss of power' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'car repairs botched' is the wordplay.
I cannot really see how this works, but
'car' could be 'rr' (Rolls Royce) and 'rr' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'with' is the link.
Can you help me to learn more?
(Other definitions for sierra that I've seen before include "Jagged mountains - code word for S" , "A range of mountains in Spain" , "Nato alphabet 'S'" , "One range" , "letter read out on the radio" .)