Fix group of ships heading in opposite direction (4)
I believe the answer is:
nail
'fix group of ships' is the definition.
'nail' can be an answer for 'fix' (I've seen this before). I am unsure of the 'group of ships' bit.
'heading in opposite direction' is the wordplay.
'heading' is a charade indicator (letters next to each other) (some letters go in front of or head others).
'in opposite' becomes 'ail' (I can't justify this - if you can you should believe this answer much more).
'direction' becomes 'N' (compass direction north).
'ail' after 'n' is 'NAIL'.
Can you help me to learn more?
(Other definitions for nail that I've seen before include "Metal fastener" , "stud" , "Hammer's target" , "Growth on digit" , "Spike, fasten" .)