Tell engineers are overdue (6)
I believe the answer is:
relate
'tell' is the definition.
(as in to tell or relate a story)
'engineers are overdue' is the wordplay.
'engineers' becomes 're' (Royal Engineers).
'are overdue' becomes 'late' (similar in meaning).
're'+'late'='RELATE'
(Other definitions for relate that I've seen before include "Give a report or show a connection" , "Marriage Guidance - report" , "Describe an event" , "Show a connection between (things)" , "Narrate or connect things" .)