The ram can be a sire (5)
I believe the answer is:
aries
'the ram' is the definition.
(I have seen 'The Ram ' mean 'aries' so perhaps 'ram' could also mean 'aries')
'can be a sire' is the wordplay.
'can be' indicates anagramming the letters.
'a'+'sire'='asire'
'asire' is an anagram of 'ARIES'.
(Other definitions for aries that I've seen before include "star group" , "Sheep" , "House" , "Constellation with sign of the ram" , "Zodiacal sign also known as the Ram" .)