Fit shelves oddly missing in loft (8)
I believe the answer is:
athletic
'fit' is the definition.
(I've seen this before)
'shelves oddly missing in loft' is the wordplay.
'oddly missing' means one should take alternating letters (letters in odd-numbered positions removed).
'in' means one lot of letters goes inside another.
'loft' becomes 'attic' (synonyms).
The alternate letters of 'shelves' are 'hle'.
'hle' put within 'attic' is 'ATHLETIC'.
(Other definitions for athletic that I've seen before include "Lithe cat (anag.)" , "Vigorously active" , "Good at physical games" , "Physically fit, strong and active" , "Active, sporty" .)