Painless treatment for dogs (8)

I believe the answer is:

spaniels

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

'painless treatment' is the wordplay.
'treatment' is an anagram indicator (the letters must be processed or treated).
'painless' is an anagram of 'SPANIELS'.

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

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app