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 "Destructive tropical grasshopper", "Destructive creature", "It strips plants", "Stripper", "Migratory crop stripper", "destructive creature", "Clouts (anag)", "Voracious African or Asian grasshopper", "Insect" and "Voracious grasshopper that travels in swarms".)