Zodiacal sign (6)
(Other definitions for pisces that I've seen before include "Twelfth sign of the zodiac, the Fish" , "Twelfth zodiacal sign" , "Spice for the Fish" , "'Sign of the zodiac, the fish (6)'" , "Fish star sign" .)
'zodiacal sign' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aries that I've seen before include "Philip -, English poet" , "star group" , "Stars" , "Sheep" , "Zodiac ram" .)