Recalled Phi, say, securing word for ‘farmyard noise’ in Chambers (9)

'chambers' is the definition.
(a roomette is a small room or chamber)

'recalled phi say securing word for farmyard noise' is the wordplay.
'recalled' says the letters should be written backwards.
'phi say' becomes 'setter' (Phi is an Independent crossword setter).
'securing' indicates putting letters inside.
'word for farmyard noise' becomes 'moo' (word for the noise made by a cow).
'setter' enclosing 'moo' is 'settemoor'.
'settemoor' reversed gives 'ROOMETTES'.

'in' acts as a link.