Tender doctor turned up in case (6)
I believe the answer is:
submit
'tender' is the definition.
(thesaurus)
'doctor turned up in case' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'turned up' says the letters should be written in reverse.
'in' means one lot of letters goes inside another.
'case' becomes 'suit' ('suit' can be a synonym of 'case').
'mb' written backwards gives 'bm'.
'bm' placed into 'suit' is 'SUBMIT'.
(Other definitions for submit that I've seen before include "Put forward for approval or yield" , "Refer for judgment or consideration" , "Give way" , "Consent" , "Present (an application)" .)