Dressed, perhaps mostly for bed (5)
I believe the answer is:
robed
'dressed' is the definition.
(robing is a kind of dressing)
'perhaps mostly for bed' is the wordplay.
'perhaps' is an anagram indicator.
'mostly' means to remove the first letter.
'for' with its first letter removed is 'or'.
'or' anagrammed gives 'ro'.
'ro'+'bed'='ROBED'
(Other definitions for robed that I've seen before include "Wearing judge's garments" , "Dressed" , "Attired" , "In a long garment" .)