Always apparently packing an extra five in a single square container (4)
I believe the answer is:
ewer
'container' is the definition.
(ewer is a kind of container)
'always apparently packing' is the wordplay.
'always' becomes 'eer' (poetic way of saying ever).
'apparently' becomes 'w' (I can't justify this - if you can you should believe this answer much more).
'packing' indicates putting letters inside.
'eer' placed around 'w' is 'EWER'.
'an extra five in a single square' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for ewer that I've seen before include "Water-jar" , "water-carrier" , "Oversized jug" , "Large pitcher" , "Large, wide-mouthed jug" .)