You could call it a strain (4)
I believe the answer is:
tune
'a strain' is the definition.
(I know that strain can be written as tune)
'you could call it' is the wordplay.
I cannot quite see how this works, but
'you' could be 'u' (commonly used in online communication) and 'u' is located in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
The remaining letters 'ne' 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 tune that I've seen before include "Song" , "Air, melody" , "Melody; adjust (engine)" , "'He who pays the piper calls the ...'" , "strain" .)