When Ted's around about, little sister stops (7)
I believe the answer is:
desists
'stops' is the definition.
(I've seen this before)
'when ted's around about little sister' is the wordplay.
'when' becomes 'is' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'around' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'little' indicates taking the first letters.
The first letter of 'sister' is 's'.
'teds' anagrammed gives 'dest'.
'is' placed into 'dest' is 'desist'.
'desist'+'s'='DESISTS'
Can you help me to learn more?
(Other definitions for desists that I've seen before include "Stops, refrains from" , "Ceases" .)