Seconds after otherwise eating balanced snack (9)
I believe the answer is:
elevenses
'snack' is the definition.
(I've seen this before)
'seconds after otherwise eating balanced' is the wordplay.
'seconds' becomes 's'.
'after' says to put letters next to each other.
'otherwise' becomes 'else' ('else' can be a synonym of 'otherwise'**).
'eating' indicates putting letters inside.
'balanced' becomes 'even' (I've seen this before).
'else' placed around 'even' is 'elevense'.
's' put after 'elevense' is 'ELEVENSES'.
(Other definitions for elevenses that I've seen before include "Mid-morning break" , "Morning snack" , "Coffee time?" , "Mid-morning refreshment" , "Soccer teams" .)