Still tucking into other special snack (9)
I believe the answer is:
elevenses
'snack' is the definition.
(I've seen this before)
'still tucking into other special' is the wordplay.
'still' becomes 'even' ('even' can be a synonym of 'still'**).
'tucking into' means one lot of letters goes inside another.
'other' becomes 'else' ('else' can be a synonym of 'other').
'special' becomes 's' (common abbreviation as in Special Air Service).
'even' put into 'else' is 'elevense'.
'elevense'+'s'='ELEVENSES'
(Other definitions for elevenses that I've seen before include "tenses found immediately before this?" , "Mid-morning refreshment" , "Mid-morning snack" , "Morning tea or coffee break" , "Refreshments" .)