Look at tree stuffed with bit of wet rubbish (7)
I believe the answer is:
'rubbish' is the definition.
(both can mean nonsense)
'look at tree stuffed with bit of wet' is the wordplay.
'look at' becomes 'eye' (I've seen this in another clue).
'tree' becomes 'ash' (ash is a kind of tree).
'stuffed with' is an insertion indicator (some letters get stuffed inside).
'bit of' suggests taking the first letters.
The first letter of 'wet' is 'w'.
'eyeash' going around 'w' is 'EYEWASH'.
(Other definitions for eyewash that I've seen before include "Optic lotion - nonsense!" , "Balderdash" , "Bunk" , "Pupils may benefit from this" , "Nonsense (informal)" .)