Carlyle so thought to contain kingdom (7)
I believe the answer is:
lesotho
'kingdom' is the definition.
(I've seen this before)
'carlyle so thought to contain' is the wordplay.
'to contain' indicates the answer is hidden within the clue (words from the clue contain the answer).
'LESOTHO' is hidden in the letters of 'carlyle so thought'.
(Other definitions for lesotho that I've seen before include "Independent kingdom, an enclave of South Africa" , "Kingdom that was formerly Basutoland" , "Landlocked country in southern Africa" , "African territory" , "He loots (anag) -- southern African kingdom" .)