Alfresco meal: be eating rotten EU crab? (8)
I believe the answer is:
'alfresco meal' is the definition.
(I've seen this before)
'be eating rotten eu crab?' is the wordplay.
'eating' indicates putting letters inside.
'rotten' indicates an anagram.
'eucrab' with letters rearranged gives 'arbecu'.
'be' placed around 'arbecu' is 'BARBECUE'.
(Other definitions for barbecue that I've seen before include "Outdoor eating occasion" , "Cuba beer for outdoor meat meal" , "Cuba beer (anag.)" , "A picnic with grilled meats" , "Grill over an open fire" .)