The one expensive motor cuts power (2,5)
I believe the answer is:
mr right
'the one' is the definition.
(both can mean the ideal partner)
'expensive motor cuts power' is the wordplay.
'expensive motor' becomes 'RR' (short for Rolls Royce).
'cuts' means one lot of letters goes inside another (some letters cut their way into a word).
'power' becomes 'might' (synonyms).
'rr' going within 'might' is 'MR RIGHT'.
(Other definitions for mr right that I've seen before include "Utopian potential husband?" , "Woman's ideal partner" , "Perfect husband" , "great match" , "Perfect man (for someone)" .)