Sign there's tooth decay, first one pulled (5)
I believe the answer is:
aries
'sign' is the definition.
(star sign)
'tooth decay first one pulled' is the wordplay.
'tooth decay' becomes 'caries' (dental caries).
'first one pulled' means to remove the first letter.
'caries' with its first letter taken away is 'ARIES'.
'there's' is the link.
(Other definitions for aries that I've seen before include "Ram star sign" , "Constellation with sign of the ram" , "A sign from Heaven" , "Philip -, English poet" , "Zodiacal sign also known as the Ram" .)