Identify a strange canister (9)
I believe the answer is:
ascertain
'identify' is the definition.
(ascertain can mean to calculate or identify)
'a strange canister' is the wordplay.
'strange' indicates an anagram.
'canister' anagrammed gives 'scertain'.
'a'+'scertain'='ASCERTAIN'
(Other definitions for ascertain that I've seen before include "Find out by making enquiries in sectarian way" , "Become aware" , "Confirm, make sure" , "settle" , "Cartesian (anag)" .)