A fraction cross inside model hotel (5)
I believe the answer is:
sixth
'a fraction' is the definition.
(sixth is a kind of fraction)
'cross inside model hotel' is the wordplay.
'cross' becomes 'x' (X is cross-shaped).
'inside' indicates putting letters inside.
'model' becomes 'sit' (synonyms).
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'x' inserted within 'sit' is 'sixt'.
'sixt'+'h'='SIXTH'
(Other definitions for sixth that I've seen before include "Beaten by five" , "Musical interval from A to F, say" , "fraction" , "ordinal" .)