Take part in play, oddly unable to be real (6)
I believe the answer is:
actual
'be real' is the definition.
(synonyms)
'take part in play oddly unable' is the wordplay.
'take part in play' becomes 'act' (I've seen this before).
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
The alternating letters of 'unable' are 'ual'.
'act'+'ual'='ACTUAL'
'to' acts as a link.
(Other definitions for actual that I've seen before include "Concrete, tangible" , "Real, not illusory" , "Real and current (6)" , "Real and existing (6)" , "Existing in fact, current" .)