A doctor said go in slow movements (7)
I believe the answer is:
adagios
'slow movements' is the definition.
(I've seen this before)
'a doctor said go' is the wordplay.
'doctor' indicates an anagram.
'said'+'go'='saidgo'
'saidgo' with letters rearranged gives 'dagios'.
'a'+'dagios'='ADAGIOS'
'in' is the link.
(Other definitions for adagios that I've seen before include "Movements in slow time" , "Slow and graceful passages of music" .)