Run in without importance in attractive fashion (8)
I believe the answer is:
prettily
'run in without importance' is the definition.
I can't judge whether this definition defines the answer.
'in attractive fashion' is the wordplay.
'in' is an insertion indicator.
'attractive' becomes 'pretty' (pretty can mean good-looking or attractive).
'fashion' becomes 'il' (I can't explain this - if you can you should believe this answer much more).
'pretty' going around 'il' is 'PRETTILY'.
Can you help me to learn more?
(Other definitions for prettily that I've seen before include "in dainty fashion" , "in cute way" .)