Behind doctor’s yard, conduct rehearsal (3,3)
I believe the answer is:
dry run
'rehearsal' is the definition.
(synonyms)
'behind doctor's yard conduct' is the wordplay.
'behind' means one lot of letters go next to another.
'doctor' becomes 'Dr' (abbreviation).
'yard' becomes 'y' (abbreviation).
'conduct' becomes 'run' (I've seen this in another clue).
'dr'+'y' is 'dry'.
'dry'+'run'='DRY RUN'
(Other definitions for dry run that I've seen before include "Test procedure like arid trot" , "Practice session in preparation for public performance" , "Rehearsal like arid trot" , "Arid trot as kind of rehearsal" , "Rehearsal, test" .)