There's no just about it

Question

Can someone help me understand this sentence? I found it in this book, where you can see the complete dialogue.

She’d seen many injured animals when she had helped her dad, and this was bad. The pony’s leg was torn open and blood was running down it. But it didn’t have to mean the end.

Ellie: ‘It’s just his tendon. Luke said.’ She looked at her uncle. [the uncle wants to kill the pony, the girl wants to save him]

Uncle: ‘There’s no just about it.’

Ellie: ‘But all he needs is rest. He might get better.’

Uncle: ‘He’s old. His time’s up.’

Can someone help me understand the meaning of the uncle's response?

Answer 1

The word 'just' is used here in the sense of 'only', 'simply' or 'no more than'. 'It's just his tendon' suggests that the injury isn't too bad.

'There's no "just" about it' (in speech we would emphasize the word) rejects the previous speaker's use of the word to diminish the seriousness of the injury: "It's not just his tendon: a damaged tendon can be very serious!"

Definition 4 of the adverb just.

(Btw, I can't open your link. From your excerpt it's hard to know who is speaking.)