Swallows, a treat first in the east and then the south (4)
I believe the answer is:
eats
'swallows' is the definition.
(I've seen this before)
'a treat first in the east and then the south' is the wordplay.
'a treat' is an anagram indicator.
'first in' indicates taking the first letters.
'then' says to put letters next to each other.
'the south' becomes 's' (abbreviation).
The first letters of 'the east and' is 'tea'.
'tea' anagrammed gives 'eat'.
'eat'+'s'='EATS'
(Other definitions for eats that I've seen before include "Provisions" , "what is on the Christmas menu" , "bits of food" , "Grazes perhaps" , "Devours - food" .)