An eleven with no score — useless getting worried (7)
I believe the answer is:
anxious
'worried' is the definition.
(I've seen this before)
'an eleven with no score useless' is the wordplay.
'eleven' becomes 'xi' (Roman numerals).
'with no score' becomes 'O' (O resembles 0, as in a score of zero).
'useless' becomes 'us' (abbreviation for unserviceable).
'an'+'xi'+'o'+'us'='ANXIOUS'
'getting' acts as a link.
(Other definitions for anxious that I've seen before include "Worried, nervous" , "Fretful, worried" , "Nervy" , "On edge" , "Jittery" .)