Surgery on Barbie's gob? (6)
I believe the answer is:
dollop
'gob?' is the definition.
(thesaurus)
'surgery on barbie's' is the wordplay.
'surgery' becomes 'op' (short for operation).
'on' says to put letters next to each other.
'barbie' becomes 'doll' (I've seen this in another clue).
'op' put after 'doll' is 'DOLLOP'.
(Other definitions for dollop that I've seen before include "Small, unmeasured amount" , "Blob" , "Quality of eg cream" , "great lump" , "Shapeless mass of soft food" .)