There's nothing in the making of hay, as sailors say (4)
I believe the answer is:
ahoy
'as sailors say' is the definition.
I can't judge whether this definition defines the answer.
'there's nothing in the making of hay' is the wordplay.
'there's' indicates putting letters inside (I've seen this in other clues).
'nothing in the making' becomes 'o' (I can't explain this - if you can you should give a lot more credence to this answer).
'of' is an anagram indicator (the answer comes from or 'of' the letters).
'hay' anagrammed gives 'ahy'.
'o' inserted inside 'ahy' is 'AHOY'.
Can you help me to learn more?
(Other definitions for ahoy that I've seen before include "Coastal land" , "Hailing term at sea" , "Call for attention at sea" , "Sailor's cry to ship" , "Nautical greeting" .)