Medicine not dispensed at the rear of the clinic (5)
I believe the answer is:
tonic
'medicine' is the definition.
(tonic is a kind of medicine)
'not dispensed at the rear of the clinic' is the wordplay.
'not dispensed at' becomes 'toni' (I can't explain this - if you can you should believe this answer much more).
'the rear of' suggests the final letters.
The final letter of 'clinic' is 'c'.
'toni'+'c'='TONIC'
Can you help me to learn more?
(Other definitions for tonic that I've seen before include "something invigorating" , "Small drink of spirits" , "something medicinal" , "something nice and fresh" , "Invigorating liquid" .)