Manage to get at a tin, possibly? (6)
I believe the answer is:
attain
'manage to get' is the definition.
(I've seen this before)
'at a tin possibly?' is the wordplay.
'possibly?' indicates an anagram (I've seen 'possibly' mean this).
'a'+'tin'='atin'
'atin' with letters rearranged gives 'tain'.
'at'+'tain'='ATTAIN'
(Other definitions for attain that I've seen before include "Succeed in reaching, achieve" , "Bring off" , "Gain with effort" , "Reach or gain" , "Reach or achieve" .)