Like pork pie, having ground nut and herb (6)
I believe the answer is:
untrue
'like pork pie having' is the definition.
I can't tell whether this definition defines the answer.
'ground nut and herb' is the wordplay.
'ground' is an anagram indicator ('grind' the letters into a new form).
'and' is a charade indicator (letters next to each other).
'herb' becomes 'rue' (rue is a herb).
'nut' is an anagram of 'unt'.
'unt'+'rue'='UNTRUE'
Can you help me to learn more?
(Other definitions for untrue that I've seen before include "Not loyal" , "Spurious" , "like the magnetic north?" , "Not faithful" , "Incorrect or false" .)