Gentleman fooling around with Net or Web (12)
I believe the answer is:
entanglement
'web' is the definition.
('entanglement' can be a synonym of 'web')
'gentleman fooling around with net' is the wordplay.
'fooling around with' is an anagram indicator.
'gentleman' with its letters mixed up with 'net' gives 'ENTANGLEMENT'.
'or' acts as a link.
(Other definitions for entanglement that I've seen before include "Ill-advised liaison" , "A complication" , "Confused state; perplexity" , "Imbroglio" .)