Search staff nurse, at first in cabin (7)
I believe the answer is:
manhunt
'search' is the definition.
(I know that manhunt is a type of search)
'staff nurse at first in cabin' is the wordplay.
'staff' becomes 'man' (as in staffing or manning a particular place).
'at first' says to take the initial letters.
'in' means one lot of letters goes inside another.
'cabin' becomes 'hut' (both can mean a small building).
The first letter of 'nurse' is 'n'.
'n' placed into 'hut' is 'hunt'.
'man'+'hunt'='MANHUNT'
(Other definitions for manhunt that I've seen before include "Search for wanted person" , "in which one wanted to be found?" , "Search for criminal" , "Pursuit of missing person" , "Police search operation" .)