One and six shillings for Latin bird (4)
I believe the answer is:
avis
'latin bird' is the definition.
(I've seen this in another clue)
'one and six shillings' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'and' means one lot of letters go next to another.
'six' becomes 'VI' (Roman numerals).
'shillings' becomes 's' (abbreviation e.g. Lsd - pounds, shillings, pence).
'a'+'vi'+'s'='AVIS'
'for' acts as a link.
(Other definitions for avis that I've seen before include "Rara --, rare bird (or car rental firm)" , "Unusual bird or extraordinary person - rara ?." .)