English old people can be reserved (7)
I believe the answer is:
engaged
'be reserved' is the definition.
(similar in meaning)
'english old people' is the wordplay.
'english' becomes 'eng' (abbreviation).
'old people' becomes 'aged' (the aged, ie elderly people).
'eng'+'aged'='ENGAGED'
'can' is the link.
(Other definitions for engaged that I've seen before include "In use" , "Fully occupied" , "Busy - fiancee" , "Absorbed" , "May as well ring off" .)