Helpful diner ordered in hurry (8)
I believe the answer is:
friendly
'helpful' is the definition.
(thesaurus)
'diner ordered in hurry' is the wordplay.
'ordered' indicates anagramming the letters.
'in' is an insertion indicator.
'hurry' becomes 'fly' (I've seen this before).
'diner' with letters rearranged gives 'riend'.
'riend' placed into 'fly' is 'FRIENDLY'.
(Other definitions for friendly that I've seen before include "prepared to talk to fellow passengers?" , "Affable" , "such a society" , "One is obviously on good terms with" , "on the same side" .)