Snake of a short species (3)
I believe the answer is:
asp
'snake' is the definition.
(asp is a kind of snake)
'a short species' is the wordplay.
'short species' becomes 'sp' (I've seen this in other clues; 'short' asks for a short form).
'a'+'sp'='ASP'
'of' acts as a link.
(Other definitions for asp that I've seen before include "A glider's what's called for" , "Cleopatra-killing snake" , "Reptile" , "One secreting poison" , "Cold-blooded killer" .)