Hammers backing you to become England football manager (6)
I believe the answer is:
ramsey
'england football manager' is the definition.
(Alf Ramsey)
'hammers backing you' is the wordplay.
'hammers' becomes 'rams'.
'backing' shows that the letters should be reversed in order.
'you' becomes 'ye' (**).
'ye' back-to-front is 'ey'.
'rams'+'ey'='RAMSEY'
'to become' is the link.
(Other definitions for ramsey that I've seen before include "IOM town" , "on the Isle of Man" .)