Thirsty doctor has last of sherry (3)
I believe the answer is:
dry
'thirsty' is the definition.
(similar in meaning)
'doctor has last of sherry' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'has' means one lot of letters go next to another.
'last of' suggests the final letters.
The final letter of 'sherry' is 'y'.
'dr'+'y'='DRY'
(Other definitions for dry that I've seen before include "off the wagon" , "Waterless" , "Desiccated" , "Lacking moisture" , "Fine" .)