Doctor's theory -- oddly found in pub (6)
I believe the answer is:
intern
'doctor's' is the definition.
(intern is a kind of doctor)
'theory oddly found in pub' is the wordplay.
'oddly' indicates alternate letters.
'found in' is an insertion indicator.
'pub' becomes 'inn' (I've seen this before).
The alternating letters of 'theory' are 'ter'.
'ter' inserted into 'inn' is 'INTERN'.
(Other definitions for intern that I've seen before include "Confine - person on work experience" , "Confine - physician in US hospital" , "Deprive of freedom" , "Novice gaining experience" , "cage" .)