Corporation accepting revised date after some delay (9)
I believe the answer is:
belatedly
'after some delay' is the definition.
(I've seen this before)
'corporation accepting revised date' is the wordplay.
'corporation' becomes 'belly' (synonyms).
'accepting' is an insertion indicator.
'revised' indicates anagramming the letters.
'date' is an anagram of 'ated'.
'belly' placed around 'ated' is 'BELATEDLY'.
(Other definitions for belatedly that I've seen before include "after some delay" , "after date" , "after usual time" , "Adverb meaning very or too late" .)