Short part of later session (5)
I believe the answer is:
terse
'short' is the definition.
(synonyms)
'part of later session' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'TERSE' is hidden within 'later session'.
(Other definitions for terse that I've seen before include "Aphoristic" , "Crisp and brief" , "Abrupt, concise" , "Short, abrupt" , "Curt among trees" .)