Brit left slyly, taking Yankee’s top hat (6)
I believe the answer is:
trilby
'hat' is the definition.
(trilby is a kind of hat)
'brit left slyly taking yankee's top' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'l' (common abbreviation) and 'l' is found within the answer.
an anagram of 'brit' is 'trib' which is within the remaining letters.
'yankee' could be 'y' (phonetic alphabet: alpha, bravo, charlie etc.) and 'y' is found in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for trilby that I've seen before include "Soft hat with indented crown" , "The singer under the control of the hypnotist Svengali" , "Impressionable singer" , "Man's soft felt hat" , "Sinatra's hat?" .)