Cloudy oil: managed to bottle that up (7)
I believe the answer is:
nebular
'cloudy' is the definition.
(similar in meaning)
'oil managed to bottle that up' is the wordplay.
'oil' becomes 'lube' (synonyms).
'managed' becomes 'ran' (both can mean organised or was in charge of).
'to bottle' indicates putting letters inside (bottle can mean to contain).
'that up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'lube' inserted within 'ran' is 'raluben'.
'raluben' written backwards gives 'NEBULAR'.
(Other definitions for nebular that I've seen before include "Hazy and formless" , "Cloudlike" , "Like clouds" , "Like dust that could be stellar" , "Cloudy" .)