Frank is in US brothel? (6)
I believe the answer is:
honest
'frank' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for honest that I've seen before include "Honourable, true" , "Sincere, upright" , "Genuine; fair" , "Truthful and dependable" , "Free of deceit and lies - truly!" .)