At that point? Working on that (7)
I believe the answer is:
thereon
'on that' is the definition.
(synonyms)
'at that point? working' is the wordplay.
'at' means one lot of letters go next to another.
'that point?' becomes 'there' (I can't justify this - if you can you should give a lot more credence to this answer).
'working' becomes 'on' (on can mean working or activated).
'there'+'on' is 'THEREON'.
Can you help me to learn more?
(Other definitions for thereon that I've seen before include "Following from the thing just mentioned" , "At that point" .)