Assistants covering small digressions (6)
I believe the answer is:
asides
'digressions' is the definition.
('aside' can be a synonym of 'digression')
'assistants covering small' is the wordplay.
'assistants' becomes 'aides' (aide is a kind of assistant).
'covering' is an insertion indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'aides' enclosing 's' is 'ASIDES'.
(Other definitions for asides that I've seen before include "Words spoken from corner of mouth" , "confidences passed on to spectators by players" , "throwaway comments" , "Stage-whispers" , "Incidental remarks" .)