Agreeing to study issue with worker (9)
I believe the answer is:
consonant
'agreeing' is the definition.
(thesaurus)
'study issue with worker' is the wordplay.
'study' becomes 'con' (I've seen this before).
'issue' becomes 'son' (issue can mean someone's offspring).
'with' says to put letters next to each other.
'worker' becomes 'ant' (worker is a type of ant).
'con'+'son'+'ant'='CONSONANT'
'to' is the link.
(Other definitions for consonant that I've seen before include "Only one of Ouida's characters is" , "Something like G, B and D" , "One of many letters" , "not I, nor you, one hears" , "Agreeing" .)