Blue ran out, like a cloud (7)
I believe the answer is:
nebular
'like a cloud' is the definition.
(I've seen this before)
'blue ran out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'blue'+'ran'='blueran'
'blueran' with letters rearranged gives 'NEBULAR'.
(Other definitions for nebular that I've seen before include "Cloudy" , "Misty" , "Like clouds" , "Like a cloud (in space)" , "Hazy and formless" .)