Give an account of soldiers and others in retreat (6)
I believe the answer is:
relate
'give an account' is the definition.
(I've seen this before)
'soldiers and others in retreat' is the wordplay.
'soldiers' becomes 're' (Royal Engineers).
'and others' becomes 'etal' (short for 'et alia', 'and others' in Latin).
'in retreat' says the letters should be written in reverse.
'etal' reversed gives 'late'.
're'+'late'='RELATE'
'of' acts as a link.
(Other definitions for relate that I've seen before include "Tell; connect" , "how to get on?" , "Describe an event" , "Give account of (story)" , "Recite - marriage guidance organisation" .)