Title seen in libraries, I reckon (3)
I believe the answer is:
sir
'title' is the definition.
(respectful address for a man)
'in libraries i reckon' is the wordplay.
'in' says the answer is hidden in the clue.
'SIR' is hidden in the letters of 'libraries i reckon'.
'seen' acts as a link.
(Other definitions for sir that I've seen before include "Form of address for a knight" , "Polite or formal address to male" , "Formal and deferential address to a man" , "Title of 1 across" , "as Winston Churchill was" .)