East European declaims sluggish carpet cleaner (6)

I believe the answer is:

slovak

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

'east european' is the definition.
'slovak' can be an answer for 'european' (I've seen this before). I am not certain of the 'east' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for slovak that I've seen before include "East European language" , "Eg, native of Bratislava" , "Central European" , "Native of European republic" , "One from Bratislava" .)

I've seen this clue in The Independent.

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