Tenor and doctor, unusually fit (5)
I believe the answer is:
drift
'tenor' is the definition.
(I've seen this before)
'doctor unusually fit' is the wordplay.
'doctor' becomes 'dr' ('Dr' can be a synonym of 'doctor'**).
'unusually' is an anagram indicator.
'fit' with letters rearranged gives 'ift'.
'dr'+'ift'='DRIFT'
'and' acts as a link.
(Other definitions for drift that I've seen before include "General trend - current travel" , "Coast" , "Bank (of snow)" , "aimless" , "Meander aimlessly" .)