Decorum in fashions? Totally gutted (7)
I believe the answer is:
modesty
'decorum' is the definition.
(thesaurus)
'fashions? totally gutted' is the wordplay.
'fashions?' becomes 'modes' ('mode' can be a synonym of 'fashion').
'gutted' says to hollow out the word (remove centre letters) (to gut something is to remove its insides).
'totally' with its centre taken out is 'ty'.
'modes'+'ty'='MODESTY'
'in' is the link.
(Other definitions for modesty that I've seen before include "Humility; decency" , "Unassumingness" , "Self-deprecating quality" , "Decorum, shyness" , "Freedom from vanity" .)