It is obvious 150 are out of order (5)
I believe the answer is:
clear
'it is obvious' is the definition.
(similar in meaning)
'150 are out of order' is the wordplay.
'150' becomes 'CL' (Roman numerals).
'out of order' is an anagram indicator.
'are' with letters rearranged gives 'ear'.
'cl'+'ear'='CLEAR'
(Other definitions for clear that I've seen before include "Acquit" , "Fine" , "Lucid, transparent" , "Jump over without contact" , "Fair - innocent" .)