Mock lines about the same toy (3,4)
I believe the answer is:
rag doll
'the same toy' is the definition.
'rag doll' can be an answer for 'toy' (I've seen this before). I'm unsure of the 'the same' bit.
'mock lines' is the wordplay.
'mock' becomes 'rag' (ragging is a kind of mocking).
'lines' becomes 'doll' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rag'+'doll'='RAG-DOLL'
'about' acts as a link.
Can you help me to learn more?
(Other definitions for rag doll that I've seen before include "plaything's required" , "Page three girl" , "Child's plaything made from scraps of fabric" , "Long-haired cat" , "Cloth plaything" .)