Crossword Genius

Car repairs botched with loss of power (6)

Ross

I believe the answer is:

sierra

I'm a little stuck... Click here to teach me more about this clue!

'loss of power' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

'car repairs botched' is the wordplay.
I cannot quite understand how this works, but
'car' could be 'rr' (Rolls Royce) and 'rr' is located in the answer.
This explanation may well be incorrect...

'with' acts as a 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" .)

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