Reflex actions in part? That’s correct (5)
I believe the answer is:
exact
'correct' is the definition.
(similar in meaning)
'reflex actions in part?' is the wordplay.
'in part?' indicates a hidden word (I've seen 'in part' mean this).
'EXACT' is hidden within 'reflex actions'.
'that's' is the link.
(Other definitions for exact that I've seen before include "Faithful" , "Precisely accurate" , "Explicit" , "Precise, accurate" , "on the money" .)