Crossword Genius

Do exercises in bad shape to begin with — they won't bring much joy (5,7)

Ross

I believe the answer is:

party poopers

I'm a little stuck... Click here to teach me more about this clue!

'won't bring much joy' is the definition.
I can't tell whether this definition defines the answer.

'do exercises in bad shape to begin with they' is the wordplay.
I cannot quite understand how this works, but
'do' could be 'party' (I've seen this before) and 'party' is found within the answer.
'exercises' could be 'pe' (Physical Education class) and 'pe' is located in the answer.
'bad' could be 'poor' (similar in meaning) and 'poor' is located in the remaining letters.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Another definition for party poopers that I've seen is " Do spoilers".)

I've seen this clue in The Guardian.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.