Shape of fancy hotel room I'd booked originally (8)
I believe the answer is:
Here is my best explanation:
'shape' is the definition.
(rhomboid is a kind of shape)
'fancy hotel room i'd booked originally' is the subsidiary indication.
'fancy' indicates an anagram.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'originally' suggests taking the first letters.
The initial letter of 'booked' is 'b'.
'hroomidb' is an anagram of 'rhomboid'.
'of' is the link.
(Other definitions for rhomboid that I've seen before include "Form of parallelogram", "Quadrilateral in which only opposite sides and angles are equal", "Parallelogram, but not square", "form", "Parallelogram of which only opposite sides and angles are equal", "Shape", "diamond" and "Describing a type of parallelogram".)