Open to exposure, nothing may be true! (5)
I believe the answer is:
outer
'open' is the definition.
(thesaurus)
'exposure nothing may be true' is the wordplay.
I cannot quite understand how this works, but
'nothing' could be 'o' (looks like zero - 0) and 'o' is present in the answer.
an anagram of 'true' is 'uter' which is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'to' is the link.
Can you help me to learn more?
(Other definitions for outer that I've seen before include "Ring furthest from the bullseye" , "Ring for double scores on a dartboard" , "Poor shot" , "Away from the centre" , "External; part of archery target" .)