…till adorable dresses turned vital? (9)
I believe the answer is:
cultivate
'till' is the definition.
(thesaurus)
'adorable dresses turned vital?' is the wordplay.
'adorable' becomes 'cute' (I've seen this in another clue).
'dresses' means one lot of letters goes inside another (dress can mean cover).
'turned' indicates an anagram.
'vital' with letters rearranged gives 'ltiva'.
'cute' going around 'ltiva' is 'CULTIVATE'.
(Other definitions for cultivate that I've seen before include "Try to get in with" , "Foster" , "Promote" , "Grow (crops)" .)