Prepare for press when it flows back (4)
I believe the answer is:
tide
'prepare' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how one could define the other.
'press when it flows back' is the wordplay.
'press when' becomes 'edi' (I can't explain this - if you can you should believe this answer much more).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'flows back' shows that the letters should be reversed in order.
'edi'+'t'='edit'
'edit' back-to-front is 'TIDE'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for tide that I've seen before include "(With time) it waits for no man" , "Sea's movement" , "Periodic water movement" , "What might carry" , "Ocean phase" .)