Pots (as we might put it) are something useful in baseball (8)
I believe the answer is:
'something useful in baseball' is the definition.
(fence used in baseball)
'pots as we might put it' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'pots' is 'stop' which is present in the answer.
The remaining letters 'back' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'are' acts as a link.
(Other definitions for backstop that I've seen before include "baseball player" , "baseball catcher" .)