Excel with an alfresco party (5)
I believe the answer is:
outdo
'excel' is the definition.
(I've seen this before)
'with an alfresco party' is the wordplay.
'with' says to put letters next to each other.
'an alfresco' becomes 'out' (an alfresco meal is eaten outside).
'party' becomes 'do' (do can informally mean a party).
'out' next to 'do' is 'OUTDO'.
(Other definitions for outdo that I've seen before include "Perform better than, be superior to" , "Br superior to (someone)" , "Overtake" , "Overcome" , "Get the better of" .)