Cruise acts erratically, bypassing Oscar (5)
I believe the answer is:
coast
'cruise' is the definition.
(thesaurus)
'acts erratically bypassing oscar' is the wordplay.
'erratically' is an anagram indicator.
'bypassing' is an insertion indicator (I've seen this in other clues).
'oscar' becomes 'o' (phonetic alphabet: alpha, bravo, charlie etc.).
'acts' with letters rearranged gives 'cast'.
'cast' placed around 'o' is 'COAST'.
(Other definitions for coast that I've seen before include "Make no effort" , "Run without power" , "Littoral region" , "Shoreline" , "See 9" .)