Monsters and thugs boxing outside of ring (7)
I believe the answer is:
gorgons
'monsters' is the definition.
(Gorgon is an example)
'thugs boxing outside of ring' is the wordplay.
'thugs' becomes 'goons' ('goon' can be a synonym of 'thug').
'boxing' indicates putting letters inside ('box' can mean contain, as in to put in a box).
'outside of' means to remove the middle letters.
'ring' with its middle taken out is 'rg'.
'goons' going around 'rg' is 'GORGONS'.
'and' acts as a link.
(Other definitions for gorgons that I've seen before include "Mythical Greek sisters whose look turned people to stone" , "Monstrous sisters" , "fierce women" , "Ugly sisters" , "Three winged sister monsters with 'hair' of writhing snakes" .)