The usual behaviour of the male bird (7)
I believe the answer is:
pattern
'the usual behaviour' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'the male bird' is the wordplay.
'the male' becomes 'pat' (I am not sure about this - if you are sure you should believe this answer much more).
'bird' becomes 'tern' (tern is a kind of bird).
'pat'+'tern'='PATTERN'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for pattern that I've seen before include "Decorative design; model" , "style" , "Template; sequence" , "Blueprint, design" , "Shape or design" .)