Secures; so don’t eat with the following three directions (7)
I believe the answer is:
fastens
'secures' is the definition.
('fasten' can be a synonym of 'secure')
'so don't eat with the following three directions' is the wordplay.
'so' becomes 'as' (e.g. phrases like 'not as tall' and 'not so tall').
'don't eat' becomes 't' (I can't justify this - if you can you should believe this answer much more).
'with' means one lot of letters go next to another.
'the following' becomes 'f' (used when citing page numbers etc).
'three directions' becomes 'ENS' (East, North and South are compass points).
'as'+'t'='ast'
'ast' put after 'f' is 'fast'.
'fast'+'ens'='FASTENS'
Can you help me to learn more?
(Other definitions for fastens that I've seen before include "Fatness (anag.)" , "fixes" , "Attaches firmly" , "Bolts" .)