Closely examine small container (4)
I believe the answer is:
scan
'closely examine' is the definition.
(to scan is to examine in detail)
'small container' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'container' becomes 'can' (can is a kind of container).
's'+'can'='SCAN'
(Other definitions for scan that I've seen before include "Browse or skin over, say book" , "Look at quickly" , "Examine (to transmit)" , "Run over" , "Take a quick look" .)