The Border's Pocket Rocket synonymous with Limerick (4)
I believe the answer is:
poet
'rocket synonymous with limerick' is the definition.
I can't tell whether this definition defines the answer.
'the border's pocket' is the wordplay.
'the border's' means to remove the middle letters (I've seen 'borders' mean this).
'pocket' with its centre removed is 'POET'.
Can you help me to learn more?
(Other definitions for poet that I've seen before include "Writer in verse form" , "Tope with a versifier" , "Maker of verses" , "Bridges possibly" , "author" .)