Dumps 500 crude containers, after dumping one (8)
I believe the answer is:
doldrums
'dumps 500 crude' is the definition.
'doldrums' can be an answer for 'dumps' (I've seen this before). I am not sure about the '500 crude' bit.
'containers after dumping one' is the wordplay.
'containers' becomes 'drums' (drum is a kind of container).
'after' says to put letters next to each other.
'dumping one' becomes 'dol' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'drums' put after 'dol' is 'DOLDRUMS'.
Can you help me to learn more?
(Other definitions for doldrums that I've seen before include "feeling of gloom" , "Belt of calms in equatorial oceans" , "Windless zone" , "State of depression" , "still under canvas here" .)