Worried sailors about section aft (6)
I believe the answer is:
astern
'aft' is the definition.
(thesaurus)
'worried sailors about section' is the wordplay.
'worried' becomes 'ate' (I've seen this before).
'sailors' becomes 'rn' (abbreviation for Royal Navy).
'about' means one lot of letters goes inside another.
'section' becomes 's' (legal abbreviation).
'ate'+'rn'='atern'
'atern' going around 's' is 'ASTERN'.
(Other definitions for astern that I've seen before include "Towards back of boat" , "Ran set (anag.)" , "Towards the back (of a ship)" , "Backward" , "(In relation to ship) behind" .)