Disassemble oil installation -- international organisation taking lead (5)
I believe the answer is:
unrig
'disassemble' is the definition.
(I've seen this in another clue)
'oil installation international organisation taking lead' is the wordplay.
'oil installation' becomes 'rig' (as in an oil rig).
'international organisation' becomes 'UN' (United Nations).
'taking lead' says to put letters next to each other (some letters go in front of others).
'rig' put after 'un' is 'UNRIG'.
(Other definitions for unrig that I've seen before include "Take down sails" , "In rug (anag.)" , "(Of a boat) strip of its mast, stays etc" , "Dismantle" , "Take tackle out" .)