If I react strangely it may be a trick (8)
I believe the answer is:
artifice
'trick' is the definition.
(I've seen this in another clue)
'if i react strangely' is the wordplay.
'strangely' indicates an anagram.
'if'+'i'+'react'='ifireact'
'ifireact' anagrammed gives 'ARTIFICE'.
'it may be a' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for artifice that I've seen before include "Clever device" , "Subtle deception" , "Race it if (anag) - cunning" , "Trick, device" , "Clever trickery" .)