Cage birds scratching tin sign (5)
I believe the answer is:
aries
'sign' is the definition.
(star sign)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for aries that I've seen before include "A sign from Heaven" , "Constellation with sign of the ram" , "Zodiacal sign also known as the Ram" , "Zodiac ram" , "Sheep" .)