See you start to rub on behind (5)
I believe the answer is:
later
'behind' is the definition.
(thesaurus)
'see you start to rub on' is the wordplay.
'see you' becomes 'late' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'start to' suggests taking the first letters.
'on' says to put letters next to each other.
The first letter of 'rub' is 'r'.
'late'+'r'='LATER'
Can you help me to learn more?
(Other definitions for later that I've seen before include "More recent" , "Following" , "After a given point in time" , "Alert (anag.)" , "Afterward, subsequent" .)