Ruminant's dash to the left of delta (5)
I believe the answer is:
eland
'ruminant's' is the definition.
(eland is a kind of ruminant)
'dash to the left of delta' is the wordplay.
'dash' becomes 'elan' (synonyms).
'to the left of' says to take the initial letters (the leftmost letter in the word).
The first letter of 'delta' is 'd'.
'elan'+'d'='ELAND'
(Other definitions for eland that I've seen before include "Led an (anag) -- antelope" , "Laden (anag.); antelope" , "Largest living antelope" , "wild creature" , "game animal" .)