Plastic syringe can't have sharpness (11)
I believe the answer is:
astringency
'sharpness' is the definition.
(thesaurus)
'plastic syringe can't' is the wordplay.
'plastic' indicates anagramming the letters (plastic can mean easily moulded).
'syringe'+'cant'='syringecant'
'syringecant' is an anagram of 'ASTRINGENCY'.
'have' is the link.
(Other definitions for astringency that I've seen before include "Sharp or bitter quality" , "caustic" , "Harshness" , "Bitterness (of taste)" , "Biting nature" .)