Place and time for migratory insect (6)
I believe the answer is:
Here is my best explanation:
'migratory insect' is the definition.
'place and time for' is the subsidiary indication.
'place' becomes 'locus'.
'and' is a charade indicator (letters next to each other).
'time for' becomes 't' (I've seen this in other clues**).
(Other definitions for locust that I've seen before include "Ravenous insect", "Migratory crop stripper", "Destructive tropical grasshopper", "Predatory grasshopper that swarms", "Voracious insect in dreaded swarms", "Voracious grasshopper that travels in swarms", "Destructive migratory insect", "Clouts (anag)", "Swarming, destructive insect" and "Voracious African or Asian grasshopper".)