Cheerless physician describes blood type (4)
I believe the answer is:
drab
'cheerless' is the definition.
(I've seen this in another clue)
'physician describes blood type' is the wordplay.
I cannot quite see how this works, but
'physician' could be 'dr' (synonyms) and 'dr' is found within the answer.
'blood type' could be 'ab' (AB is an example) and 'ab' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for drab that I've seen before include "Drearily dull; slattern" , "Dreary and colourless" , "Dowdy" , "Dingy - shabby" , "Shabby; a slattern (arch.)" .)