8 A. Topless bloke to bang on about bikini bottoms; who's a lunatic, eh?
The first entry is the answer to the second half. Just an anagram (lunatic) of the two preceding words. The definition is 'Eh?'
For those without the puzzle, there's a shared letter, not given by wordplay.
Second entry - bikini bottoms. Topless = remove the first letter from a word meaning 'bloke' + a word meaning 'bang on about'.