A thousand of us loved one (5)
I believe the answer is:
amour
'loved one' is the definition.
(I've seen this before)
'a thousand of us' is the wordplay.
'thousand' becomes 'm' ('m' can be a synonym of 'thousand').
'of us' becomes 'our' (I've seen this before).
'a'+'m'+'our'='AMOUR'
(Other definitions for amour that I've seen before include "French lover" , "(Illicit) sexual relationship" , "A secret love affair in France" , "Affair of the heart" , "Loved one (French)" .)