Poetry lacking a writer; or, an essay (3)
I believe the answer is:
try
'an essay' is the definition.
(thesaurus)
'poetry lacking a writer' is the wordplay.
'lacking' suggests deleting specific letters.
'a writer' becomes 'poe' (Edgar Allan Poe).
'poetry' with 'poe' taken away is 'TRY'.
'or' is the link.
(Other definitions for try that I've seen before include "Four rugby points" , "Judge" , "Make severe demands on" , "Aim" , "Test; attempt" .)