Seated outside clubs, Hesse emptied small bag (6)
I believe the answer is:
sachet
'small bag' is the definition.
(I've seen this before)
'seated outside clubs hesse emptied' is the wordplay.
'seated' becomes 'sat' ('sit' can be a synonym of 'seat').
'outside' indicates putting letters inside.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'emptied' means to remove the middle letters.
'hesse' with its middle taken out is 'he'.
'c'+'he'='che'
'sat' enclosing 'che' is 'SACHET'.
(Other definitions for sachet that I've seen before include "Small bag with sweet-smelling substance" , "'Small soft packet, of pot-pourri perhaps (6)'" , "Small bag or sealed plastic pack" , "Small bag - chaste (anag)" , "Small sealed packet" .)