Small present containing soft ball (6)
I believe the answer is:
sphere
'ball' is the definition.
(thesaurus)
'small present containing soft' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'present' becomes 'here' ('here' can be similar in meaning to 'present').
'containing' means one lot of letters goes inside another.
'soft' becomes 'p' (musical abbreviation for 'piano').
's'+'here'='shere'
'shere' enclosing 'p' is 'SPHERE'.
(Other definitions for sphere that I've seen before include "Vault of heaven" , "Ball or field of influence" , "Field; globe" , "Ball, orb" , "Solid figure - range of activity" .)