What a cheque meant, as you'll have realised (4)
I believe the answer is:
cash
'what a cheque meant' is the definition.
I can't judge whether this definition defines the answer.
'as you'll have realised' is the wordplay.
I cannot really see how this works, but
'as' is found in the answer.
The remaining letters 'ch' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for cash that I've seen before include ""Readies"" , "Funds" , "bread" , "Till" , "Hard currency" .)