Party slump relates to extreme indiscipline - this might come precisely as a shot in the arm (6)
I believe the answer is:
dosage
'extreme indiscipline this might come precisely as a shot in the arm' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'party slump relates' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'slump' becomes 'sag' (I've seen this before).
'relates' becomes 'e' (I can't explain this - if you can you should give a lot more credence to this answer).
'do'+'sag'+'e'='DOSAGE'
'to' is the link.
Can you help me to learn more?
(Other definitions for dosage that I've seen before include "Quantity of medication" , "Medicine administered" , "Measured amount of medicine to be taken" , "Administered amount of drug" , "Prescribed quantity of medicine" .)