Spurs soar after developing boxing exercise (7)
I believe the answer is:
arouses
'spurs' is the definition.
'soar after developing boxing exercise' is the wordplay.
'after developing' indicates anagramming the letters.
'boxing' means one lot of letters goes inside another ('box' can mean contain, as in to put in a box).
'exercise' becomes 'use' ('use' can be a synonym of 'exercise'**).
'soar' is an anagram of 'aros'.
'aros' placed around 'use' is 'AROUSES'.
(Other definitions for arouses that I've seen before include "Stimulates" , "gets excited" , "Inspires" .)