Very small container by end of quay (4)
I believe the answer is:
tiny
'very small' is the definition.
(I've seen this before)
'container by end of quay' is the wordplay.
'container' becomes 'tin' (tin is a kind of container**).
'by' is a charade indicator (letters next to each other).
'end of' suggests the final letters.
The final letter of 'quay' is 'y'.
'tin'+'y'='TINY'
(Other definitions for tiny that I've seen before include "Minuscule" , "Wee" , "Extremely small" , "Miniature" , "Really small" .)