Bird is a layer -- 100 eggs laid for starters (7)
I believe the answer is:
tiercel
'bird' is the definition.
(tiercel is a kind of bird)
'layer 100 eggs laid for starters' is the wordplay.
'layer' becomes 'tier' (tier is a kind of layer).
't00' becomes 'c' (Roman numeral).
'for starters' suggests taking the first letters.
The initial letters of 'eggs laid' is 'el'.
'tier'+'c'+'el'='TIERCEL'
'is a' acts as a link.
(Other definitions for tiercel that I've seen before include "It flies" , "See hawk" .)