No tough guy, one's undesirable in bed (4)
I believe the answer is:
weed
'undesirable in bed' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'no tough guy one's' is the wordplay.
I cannot quite understand how this works, but
'guy' could be 'ed' (short for Edward) and 'ed' is found in the answer.
The remaining letters 'we' 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 weed that I've seen before include "Wild unwanted plant - tobacco?" , "pot" , "Marijuana (slang)" , "Useless plant - useless person" , "Troublesome plant" .)