Slavery unlikely to be found around Croatia (6)
I believe the answer is:
thrall
'slavery' is the definition.
(synonyms)
'unlikely to be found around croatia' is the wordplay.
'unlikely' becomes 'tall' (I've seen this before).
'to be found around' means one lot of letters goes inside another.
'croatia' becomes 'hr' (I can't justify this - if you can you should give a lot more credence to this answer).
'tall' enclosing 'hr' is 'THRALL'.
Can you help me to learn more?
(Other definitions for thrall that I've seen before include "The state of being under the control of another person" , "subjection" , "captivity" , "Bondage, enslavement" , "State of being in another person''s power" .)