Lovely planet revolving around a sun (8)
I believe the answer is:
pleasant
'lovely' is the definition.
(I've seen this before)
'planet revolving around a sun' is the wordplay.
'revolving' is an anagram indicator (letters turning or twisting around).
'around' means one lot of letters goes inside another.
'sun' becomes 's'.
'planet' with letters rearranged gives 'pleant'.
'a'+'s'='as'
'pleant' placed around 'as' is 'PLEASANT'.
(Other definitions for pleasant that I've seen before include "Enjoyable, nice" , "Satisfying, likeable" , "Likeable, friendly" , "Nice, satisfying" , "Lovely" .)