False step leading to oil spill in capital (7)
I believe the answer is:
tripoli
'capital' is the definition.
(capital of Libya)
'false step leading to oil spill' is the wordplay.
'false step' becomes 'trip' (as in tripping over).
'leading to' says to put letters next to each other (some letters go before or lead others).
'spill' is an anagram indicator (letters spilled or knocked around).
'oil' anagrammed gives 'oli'.
'trip'+'oli'='TRIPOLI'
'in' is the link.
(Other definitions for tripoli that I've seen before include "where there's been regime change" , "city on the Mediterranean" , "Libya's capital" , "Libyan city" , "North African city" .)