Spurs game I must lampoon, ironically at first (7)
I believe the answer is:
stimuli
'spurs' is the definition.
(plural of stimulus, a spur or cause of something)
'game i must lampoon ironically at first' is the wordplay.
'game' indicates an anagram (solving anagrams is a game).
'at first' indicates taking the first letters.
The initial letters of 'lampoon ironically' is 'li'.
'i'+'must'='imust'
'imust' anagrammed gives 'stimu'.
'stimu'+'li'='STIMULI'
(Other definitions for stimuli that I've seen before include "Incentives to action" , "Things that rouse one to activity" , "Jogs" , "Things provoking reactions" , "Things that cause a response" .)