Remained utterly sober (6)
I believe the answer is:
stayed
'remained' is the definition.
(staying is a kind of remaining)
'utterly sober' is the wordplay.
'utterly' shows a homophone (sound like) (as uttered).
'sober' becomes 'staid' (synonyms).
'staid' sounds like 'STAYED'.
(Other definitions for stayed that I've seen before include "Hung about" , "Tarried" , "Remained, propped up" , "Remained or posponed" , "Remained or deferred" .)