Very big tenor followed by ample bird (7)
I believe the answer is:
ostrich
'bird' is the definition.
(ostrich is a kind of bird)
'very big tenor followed by ample' is the wordplay.
'very big' becomes 'os' (abbreviation for outsize).
'tenor' becomes 't'.
'followed by' says to put letters next to each other.
'ample' becomes 'rich' ('rich' can be a synonym of 'ample').
'os'+'t'+'rich'='OSTRICH'
(Other definitions for ostrich that I've seen before include "Long-necked bird" , "The head-in-the-sand bird" , "A bird for the shirt co." , "The biggest bird, can't fly" , "with a big nest egg" .)