In the midst of anxiety, a case for doctor (7)
I believe the answer is:
amongst
'in the midst of' is the definition.
(I've seen this before)
'anxiety a case for doctor' is the wordplay.
'anxiety' becomes 'angst' (Angst is an example).
'a case for' indicates putting letters inside.
'doctor' becomes 'mo' (medical officer).
'angst' enclosing 'mo' is 'AMONGST'.
(Other definitions for amongst that I've seen before include "Within the group of" , "Famous novel by John McGahern: '... Women'" , "In the midst of" , "Surrounded by" , "Together with" .)