No people, for instance, will enter it (8)
I believe the answer is:
negation
'no' is the definition.
(thesaurus)
'people for instance will enter it' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
'for instance' could be 'eg' (short for 'exempli gratia', 'for example' in Latin) and 'eg' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for negation that I've seen before include "people" , "opposite" , "One giant turns out to be a denial" , "Contradiction" , "Disaffirmation" .)