### Clue: WI song so neglected in Brussels it upset oil suppliers (9)
### Answer: EUCALYPTI 
 ### Explanation: Definition: oil suppliers
 "calypso"(a kind of song or music originally from the WI/West Indies) **minus**(… neglected) "so" **contained in**(in) [EU(abbrev. for the European Union, synonymous with Brussels, where the organisation's headquarters is in) + **reversal of**(… upset) IT].
Defn: Plural of the tree from which eucalyptus oil is extracted/supplied.