Cattle company was heartless (4)
I believe the answer is:
cows
'cattle' is the definition.
(synonyms)
'company was heartless' is the wordplay.
'company' becomes 'co' (abbreviation).
'heartless' says to hollow out the word (remove centre letters).
'was' with its centre taken out is 'ws'.
'co'+'ws'='COWS'
(Other definitions for cows that I've seen before include "Female bovines" , "Domestic cattle" , "Domesticated bovines" , "Kine" , "Milk providers" .)