Gentleman will abruptly lift this up. (3)
I believe the answer is:
sir
'gentleman' is the definition.
(a man may be addressed as sir)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sir that I've seen before include "Form of address for a knight" , "Feted fellow" , "address to teacher" , "Male form of address" , "Respectful address for a man" .)