Confident like Bob, and frightfully rude (7)
I believe the answer is:
assured
'confident' is the definition.
(similar in meaning)
'like bob and frightfully rude' is the wordplay.
'like' becomes 'as'.
'bob' becomes 's' (abbreviation for shilling - 'bob' before 1971).
'and' means one lot of letters go next to another.
'frightfully' is an anagram indicator (I've seen this in other clues).
'rude' is an anagram of 'ured'.
'as'+'s'+'ured'='ASSURED'
(Other definitions for assured that I've seen before include "Confident - certain" , "without doubt" , "Informed with certainty and confidence" , "Secured" , "Confident and self-possessed" .)