Like the line back from Poole? (4)
I believe the answer is:
loop
'poole?' is the definition.
Both the answer and definition are singular nouns.
Maybe there's a link between them I don't understand?
'like the line back' is the wordplay.
'like' becomes 'poo' (I can't justify this - if you can you should give a lot more credence to this answer).
'the line' becomes 'l'.
'back' shows that the letters should be reversed in order.
'poo'+'l'='pool'
'pool' backwards is 'LOOP'.
'from' is the link.
Can you help me to learn more?
(Other definitions for loop that I've seen before include "I cross myself" , "Endless strip of tape" , "Noose" , "Oval-shaped coil" , "Shape formed by a closed curve that does not intersect itself" .)