It means nothing for fellows to get a letter from ladies (4)
I believe the answer is:
omen
'it means nothing' is the definition.
The definition suggests a singular noun which matches the answer.
'fellows to get a letter from ladies' is the wordplay.
I cannot really understand how this works, but
'fellows' could be 'men' (fellow can mean a man) and 'men' is found within the answer.
'letter' could be 'o' and 'o' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for omen that I've seen before include "Foreboding" , "Augury, portent" , "Harbinger, portent" , "Warning - sign" , "Prognostication" .)