Sign used in battle occasionally (3)
I believe the answer is:
leo
'sign' is the definition.
(star sign)
'in battle occasionally' is the wordplay.
'in' indicates a hidden word.
'LEO' is hidden within 'battle occasionally'.
'used' is the link.
(Other definitions for leo that I've seen before include "Lion sign of the Zodiac" , "one of several popes" , "house" , "Horoscope sign" , "Fifth sign of the zodiac" .)