Dogs having painless operations (8)

I believe the answer is:

spaniels

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

'dogs' is the definition.
(spaniel is a kind of dog)

'painless operations' is the wordplay.
'painless' can be anagrammed to 'SPANIELS'.
However, I'm unsure how this is indicated.

'having' is the link.

Can you help me to learn more?

(Another definition for spaniels that I've seen is " The dogs can be oddly painless".)

I've seen this clue in The Irish Independent.

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