Temperature inside star is to stupefy (4)
I believe the answer is:
stun
'is to stupefy' is the definition.
(I've seen this in another clue)
'temperature inside star' is the wordplay.
'temperature' becomes 't' (abbreviation).
'inside' is an insertion indicator.
'star' becomes 'sun' (the Sun is a star).
't' placed within 'sun' is 'STUN'.
(Other definitions for stun that I've seen before include "Daze, paralyse" , "cause amazement" , "Make dazed or numb" , "Amaze; knock senseless" , "Make senseless or dizzy with a blow" .)