Pleasant disposing of new cold dessert (3)
I believe the answer is:
ice
'cold dessert' is the definition.
(eg an ice lolly)
'pleasant disposing of new' is the wordplay.
'pleasant' becomes 'nice' (associated in meaning).
'disposing of' is a deletion indicator.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'nice' with 'n' removed is 'ICE'.
(Other definitions for ice that I've seen before include "Cold stuff used in enticement" , "Block" , "Diamonds (slang)" , "engine" , "Constituent of 2dn" .)