Theresa seen with man, married? It's chaos! (6)
I believe the answer is:
mayhem
'chaos' is the definition.
(I've seen this in another clue)
'theresa seen with man married?' is the wordplay.
'theresa' becomes 'may' (I can't justify this - if you can you should believe this answer much more).
'seen with' is a charade indicator (letters next to each other).
'man' becomes 'he' (he refers to a man).
'married?' becomes 'm' (abbreviation, e.g. in genealogy).
'may'+'he'+'m'='MAYHEM'
'it's' is the link.
Can you help me to learn more?
(Other definitions for mayhem that I've seen before include "wild state" , "Havoc, violent disturbance" , "Carnage" , "Extreme disorder" , "Violent destruction of confusion" .)