Intern bustling around hospital, becoming scrawnier (7)
I believe the answer is:
thinner
'scrawnier' is the definition.
('thin' can be similar in meaning to 'scrawny')
'intern bustling around hospital' is the wordplay.
I cannot quite see how this works, but
'hospital' could be 'h' (abbreviation for hospital on maps) and 'h' is found in the answer.
an anagram of 'intern' is 'tinner' which is located in the remaining letters.
No letters remain.
This explanation may well be incorrect...
'becoming' acts as a link.
Can you help me to learn more?
(Other definitions for thinner that I've seen before include "More sparse" , "Diluting agent" , "less strong" , "what one adds to paint" , "Diluting solvent" .)