Do come by to collect that girl (3-8)
I believe the answer is:
get-together
'collect that girl' is the definition.
'get together' can be an answer for 'collect' (thesaurus). I am not sure about the remainder of the definition.
'do come by to' is the wordplay.
'do come' becomes 'get' ('get' can be a synonym of 'come').
'by' means one lot of letters go next to another.
'to' becomes 'together' (I can't justify this - if you can you should give a lot more credence to this answer).
'get'+'together'='GET-TOGETHER'
Can you help me to learn more?
(Other definitions for get-together that I've seen before include "An informal party" , "Assemble" , "Informal meeting" , "informal social gathering" .)