A number of people possibly sit and tend to shift about (7)
I believe the answer is:
dentist
'a number of people possibly sit' is the definition.
I can't judge whether this definition defines the answer.
'tend to shift about' is the wordplay.
'to shift' indicates anagramming the letters.
'about' becomes 'ist' (I can't justify this - if you can you should give a lot more credence to this answer).
'tend' is an anagram of 'dent'.
'dent'+'ist'='DENTIST'
'and' is the link.
Can you help me to learn more?
(Other definitions for dentist that I've seen before include "Tooth expert" , "Teeth specialist" , "expert in oral examination" , "Oral surgeon" , "Occasional driller" .)