Drug stops camel mostly developing germs (8)
I believe the answer is:
bacteria
'germs' is the definition.
(I've seen this before)
'drug stops camel mostly' is the wordplay.
'drug' becomes 'e' (E is another name for ecstasy).
'stops' indicates putting letters inside (stopping can mean blocking a gap).
'camel' becomes 'Bactrian camel' (Bactrian camel is an example).
'mostly' means to remove the last letter (most but not all of the word).
'bactrian' with its last letter taken off is 'bactria'.
'e' going within 'bactria' is 'BACTERIA'.
'developing' acts as a link.
(Other definitions for bacteria that I've seen before include "Single cell micro-organisms" , "source of disease" , "Single-celled organisms" , "Microscopic organisms, can carry disease" , "Micro-organisms, often pathogens" .)