Girl in lifestyle magazine, ultimate in fashion (5)
I believe the answer is:
ellen
'girl' is the definition.
'lifestyle magazine ultimate in fashion' is the wordplay.
'lifestyle magazine' becomes 'Elle'.
'ultimate in' indicates one should take the final letters.
The final letter of 'fashion' is 'n'.
'elle'+'n'='ELLEN'
'in' acts as a link.
(Other definitions for ellen that I've seen before include "-- DeGeneres, US actress" , "MacArthur, round-the-world yachtswoman" , "Dame - Terry, English actress" , "Woman" , "Dame - - Macarthur (naut.)" .)