Peers squeal when excited (6)
I believe the answer is:
equals
'peers' is the definition.
('equal' can be a synonym of 'peer')
'squeal when excited' is the wordplay.
'when excited' indicates an anagram.
'squeal' with letters rearranged gives 'EQUALS'.
(Other definitions for equals that I've seen before include "Those with the same status, rights, etc." , "Is identical or equivalent to" , "Persons of the same rank, for instance" , "They're at the same level" , "sign" .)