A sign that one may be getting a rise (5)
I believe the answer is:
aries
'a sign' is the definition.
(star sign)
'one may be getting a rise' is the wordplay.
'one may' indicates anagramming the letters (I've seen 'might' mean this (I've seen this in other clues)).
'be getting' says to put letters next to each other.
'a' put after 'rise' is 'risea'.
'risea' anagrammed gives 'ARIES'.
'that' acts as a link.
(Other definitions for aries that I've seen before include "Constellation with sign of the ram" , "First sign of the zodiac" , "Philip -, English poet" , "Stars" , "Sheep" .)