Chair backs to contain ultimate in sick bags (5)
I believe the answer is:
takes
'bags' is the definition.
(bag can mean to take or obtain)
'chair backs to contain ultimate in sick' is the wordplay.
'chair' becomes 'seat' (something to sit on).
'backs' says the letters should be written in reverse.
'to contain' indicates putting letters inside.
'ultimate in' says to take the final letters.
The final letter of 'sick' is 'k'.
'seat' backwards is 'taes'.
'taes' enclosing 'k' is 'TAKES'.
(Other definitions for takes that I've seen before include "Removes" , "Filmed scenes" , "Steals" , "sections of film" , "Seizes" .)