Herb's right - it's not so difficult (7)
I believe the answer is:
simpler
'not so difficult' is the definition.
I can't judge whether this defines the answer.
'herb's right' is the wordplay.
I cannot really understand how this works, but
'right' could be 'r' (common abbreviation) and 'r' is found within the answer.
'herb' could be 'simple' (simple is a kind of herb) and 'simple' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'it's' is the link.
Can you help me to learn more?
(Other definitions for simpler that I've seen before include "More easy" , "That wasn't so hard!)" , "Easier" , "Less complicated or complex" .)