Trade fair has allowed for nothing specific (8)
I believe the answer is:
explicit
'nothing specific' is the definition.
'explicit' can be an answer for 'specific' (I've seen this before). I'm unsure of the 'nothing' bit.
'trade fair has allowed' is the wordplay.
'trade fair has' becomes 'exp' (I can't justify this - if you can you should believe this answer much more).
'allowed' becomes 'licit' (I've seen this before).
'exp'+'licit'='EXPLICIT'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for explicit that I've seen before include "full detail" , "'Stated clearly, with no room for confusion (8)'" , "Clearly shown or stated" , "Stated or shown directly, not ambiguous" , "well defined" .)