Doctor satisfied in there, getting right item used in diagnosis (11)
I believe the answer is:
thermometer
'item used in diagnosis' is the definition.
(device for taking a patient's temperature)
'doctor satisfied in there getting right' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'satisfied' becomes 'met' (as in 'met the conditions of his contract').
'in' means one lot of letters goes inside another.
'getting right' becomes 'r' (I've seen this in other clues).
'mo'+'met'='momet'
'momet' inserted into 'there' is 'thermomete'.
'thermomete'+'r'='THERMOMETER'
(Other definitions for thermometer that I've seen before include "Instrument for measuring temperature" , "Temperature gauge" , "Temperature-measuring instrument" , "Device measuring temperature" , "Instrument with mercury or alcohol" .)