Sells the rest out, possibly, for just a single pound (7)

'sells' is the definition.
(retailing is a kind of selling)

'rest out possibly for just a single pound' is the wordplay.
I cannot really understand how this works, but
'a' is present in the answer.
'single' could be 'i' (one) and 'i' is found in the answer.
'pound' could be 'l' (the pound sign is based on an L) and 'l' is found in the answer.
an anagram of 'rest' is 'rets' which is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...

'the' acts as a link.

Can you help me to learn more?