Distance raced needs good energy (5)
I believe the answer is:
range
'distance' is the definition.
(thesaurus)
'raced needs good energy' is the wordplay.
'raced' becomes 'ran' ('run' can be a synonym of 'race').
'needs' means one lot of letters go next to another.
'good' becomes 'g' (abbreviation).
'energy' becomes 'e' (physics symbol as in E=mc2).
'ran'+'g'+'e'='RANGE'
(Other definitions for range that I've seen before include "Scope; ambit" , "Compass - scope" , "Set < compass" , "Amplitude" , "Number of items in a series" .)