Hostile crowds make headmistress Juliet quit jobs (4)
I believe the answer is:
mobs
'hostile crowds' is the definition.
'mobs' can be an answer for 'crowds' (mob is a kind of crowd). I'm not sure about the 'hostile' bit.
'headmistress juliet quit jobs' is the wordplay.
'headmistress' becomes 'm' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'juliet' becomes 'J' (phonetic alphabet: alpha, bravo, charlie etc.).
'quit' suggests deleting specific letters.
'jobs' with 'j' removed is 'obs'.
'm'+'obs'='MOBS'
'make' acts as a link.
Can you help me to learn more?
(Other definitions for mobs that I've seen before include "Disorderly crowds of people" , "Unruly crowds" , "riotous assemblies" .)