Fortunate girl sheltering king (5)
I believe the answer is:
lucky
'fortunate' is the definition.
(similar in meaning)
'girl sheltering king' is the wordplay.
'girl' becomes 'lucy' (girl's name).
'sheltering' indicates putting letters inside.
'king' becomes 'K' (abbreviation for king in chess).
'lucy' going around 'k' is 'LUCKY'.
(Other definitions for lucky that I've seen before include "Serendipitous" , "Game where prizes are picked from a tub" , "Auspicious" , "Fortunate" , "by chance" .)