Each top guy lets in some small birds (7)
I believe the answer is:
eaglets
'some small birds' is the definition.
(I've seen this before)
'each top guy lets' is the wordplay.
'each' becomes 'ea' (abbreviation).
'top' indicates taking the first letters (in a down clue, the first letter is top).
The first letter of 'guy' is 'g'.
'ea'+'g'+'lets'='EAGLETS'
'in' is the link.
(Other definitions for eaglets that I've seen before include "birds early in life" , "Small birds" .)