Recover; assembly (5)
I believe the answer is:
I believe this clue is a double definition.
'recover' is the first definition.
(I know that rally is a more specific form of the action recover)
'assembly' is the second definition.
(I've seen this in other clues)
(Other definitions for rally that I've seen before include "Get-together" , "Recover; sequence of shots" , "Mass meeting; car race" , "Bring together for a purpose, troops perhaps" , "Recuperate in gathering" .)