Surprise has fans coming back (4)
I believe the answer is:
stun
'surprise' is the definition.
(stunning is a kind of surprising)
'fans coming back' is the wordplay.
'fans' becomes 'nuts' (both can mean enthusiasts).
'coming back' is a reversal indicator.
'nuts' written backwards gives 'STUN'.
'has' is the link.
(Other definitions for stun that I've seen before include "Daze, overwhelm" , "what a cracker may do?" , "Daze, paralyse" , "Confuse" , "Stupefy - daze" .)