Demanding individual, ultimately manager to you and me (7)
I believe the answer is:
onerous
'demanding' is the definition.
(onerous means difficult or demanding)
'individual ultimately manager to you and me' is the wordplay.
'individual' becomes 'one' (an individual is one person).
'ultimately' indicates one should take the final letters.
'you and me' becomes 'us'.
The final letters of 'manager to' are 'ro'.
'one'+'ro'+'us'='ONEROUS'
(Other definitions for onerous that I've seen before include "Challenging" , "weight" , "Heavy and hard to bear" , "Effortful" , "'Heavy, burdensome (7)'" .)