It’s turned to rain, when you waken up (4)
I believe the answer is:
stir
'waken up' is the definition.
'stir' can be an answer for 'waken' (I've seen this in another clue). I am not certain of the 'up' bit.
'it's turned to rain when you' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
The remaining letters 'sir' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for stir that I've seen before include "Commotion to mix" , "Whisk or make a move" , "bird" , "Agitate; wake from sleep" , "Ladies' underwear" .)