Site Celts developed to produce plums (9)

I believe the answer is:

testicles

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

'produce plums' is the definition.
Although both the answer and definition are plural nouns, I cannot understand how one could define the other.

'site celts developed' is the wordplay.
'developed' indicates anagramming the letters.
'site'+'celts'='sitecelts'
'sitecelts' is an anagram of 'TESTICLES'.

'to' acts as a link.

Can you help me to learn more?

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.