Isolated - perhaps Messi's lost one yard (6)
I believe the answer is:
lonely
'isolated' is the definition.
(on one's own)
'messi's lost one yard' is the wordplay.
'messi' becomes 'Lionel' (footballer Lionel Messi).
'lost' indicates named letters should be taken away.
'one' becomes 'i' (Roman numeral).
'yard' becomes 'y' (abbreviation).
'lionel' with 'i' removed is 'lonel'.
'lonel'+'y'='LONELY'
'perhaps' acts as a link.
(Other definitions for lonely that I've seen before include "withdrawn" , "Unfrequented" , "Unhappily unattached persons?" , "''It's so ... 'round the 31 across of Athenry'' (song)" , "Lacking companionship" .)