Just what the doctor ordered (4)
'just what the doctor ordered' is the definition.
(I've seen this in another clue)
'doctor ordered' is the wordplay.
'doctor' becomes 'd' (eg in PhD, Doctor of Philosophy).
'ordered' becomes 'ose' (I can't justify this - if you can you should believe this answer much more).
'd'+'ose'='DOSE'
Can you help me to learn more?
(Other definitions for dose that I've seen before include "Measure of medicine" , "some Viagra, perhaps?" , "Give drugs to (a person)" , "Medicinal quantity" , "Measure (med.)" .)
(Other definitions for doses that I've seen before include "Quanitites of medicine" , "Prescribed amounts of medication" , "Prescribed amounts of medicine" , "Prescribed quantities of medicine" , "Medicine measures" .)