Strong container holds ten (6)
I believe the answer is:
potent
'strong' is the definition.
(I know this)
'container holds ten' is the wordplay.
'container' becomes 'pot' (pot is a kind of container).
'holds' is an insertion indicator.
'pot' going around 'ten' is 'POTENT'.
(Other definitions for potent that I've seen before include "Concentrated or strong, like liquor" , "Powerful like strong drink" , "Strong in operation" , "Top Ten (anag.)" , "Strong or concentrated, like some drink" .)