Have control of backup groups carrying spades (7)
I believe the answer is:
possess
'have control of' is the definition.
(someone possessed by something is controlled by it)
'backup groups carrying spades' is the wordplay.
'backup groups' becomes 'posses' (historically, groups backing up a sheriff).
'carrying' is an insertion indicator.
'spades' becomes 's' (abbreviation in card games).
'posses' placed around 's' is 'POSSESS'.
(Other definitions for possess that I've seen before include "Consume" , "Own, keep" , "Have and hold" , "Have ownership of" , "Have - control" .)