Transmissible disease? College head bearing identifying mark (9)
I believe the answer is:
contagion
'transmissible disease?' is the definition.
'contagion' can be an answer for 'disease?' (contagion is a kind of disease). I'm not sure about the 'transmissible' bit.
'college head bearing identifying mark' is the wordplay.
I cannot really understand how this works, but
'college' could be 'c' and 'c' is found in the answer.
'bearing' could be 'n' (north is a compass bearing) and 'n' is present in the answer.
'mark' could be 'tag' (synonyms) and 'tag' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for contagion that I've seen before include "Communication of disease by close contact" , "Infection" , "cause of widespread ill-feeling" , "Cognation (anag.)" .)