Tease lecturer about silly old soft toy (3,4)
I believe the answer is:
rag doll
'soft toy' is the definition.
(I've seen this before)
'tease lecturer about silly old' is the wordplay.
'tease' becomes 'rag' (synonyms).
'lecturer' becomes 'l' (abbreviation for lecturer).
'about' is an insertion indicator.
'silly' indicates anagramming the letters.
'old' is an anagram of 'dol'.
'l' going into 'dol' is 'doll'.
'rag'+'doll'='RAG-DOLL'
(Other definitions for rag doll that I've seen before include "plaything's required" , "soft toy" , "Toy made with scraps of cloth etc" , "Page three girl" , "worthless toy" .)