We are due fish for a change, having beans regularly for so long (3,11)
I believe the answer is:
auf wiedersehen
'for so long' is the definition.
(synonyms)
'we are due fish for a change having beans regularly' is the wordplay.
'for a change' indicates an anagram.
'having' says to put letters next to each other.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'beans' are 'en'.
'we'+'are'+'due'+'fish'='weareduefish'
'weareduefish' with letters rearranged gives 'aufwiederseh'.
'aufwiederseh'+'en'='AUF WIEDERSEHEN'
(Other definitions for auf wiedersehen that I've seen before include "Wanting to say farewell" , "see you" , "so long in parts of Europe" .)