"Virtually the last resort," the doctor interposed (6)
I believe the answer is:
almost
'virtually' is the definition.
(synonyms)
'last resort the doctor interposed' is the wordplay.
I cannot quite understand how this works, but
'doctor' could be 'mo' (medical officer) and 'mo' is located in the answer.
an anagram of 'last' is 'alst' which is within the left over letters.
This accounts for all the letters.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for almost that I've seen before include "Not entirely" , "Well-nigh" , "As good as" , "practically" , "Slightly short of" .)