The bird got into one biscuit tin (4)
I believe the answer is:
ibis
'the bird' is the definition.
(ibis is a kind of bird)
'into one biscuit tin' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
The remaining letters 'bis' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'got' acts as a link.
Can you help me to learn more?
(Other definitions for ibis that I've seen before include "State of central US, capital Lincoln" , "Bird, sacred to ancient Egyptians" , "Wading bird sacred to the Egyptians" , "Wader worshipped by ancient Egyptians" , "Bird venerated by ancient Egyptians" .)