Not those snaring men, I suppose (8)
I believe the answer is:
theorise
'suppose' is the definition.
('theorise' can be a synonym of 'suppose')
'not those snaring men i' is the wordplay.
'not those' becomes 'these' (I've seen this before).
'snaring' means one lot of letters goes inside another.
'men' becomes 'or' (I've seen this in other clues).
'or'+'i'='ori'
'these' going around 'ori' is 'THEORISE'.
(Other definitions for theorise that I've seen before include "Suppose" , "Form of hypothesis or conjecture" , "Express ideas" , "Form view" , "Conjecture, hypothesise" .)