Charlie avoids metaphysics that's tricky to understand (10)
I believe the answer is:
sympathise
'understand' is the definition.
(I know that understand can be written as sympathise)
'charlie avoids metaphysics that's tricky' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet).
'avoids' indicates named letters should be taken away.
'that's tricky' indicates anagramming the letters.
'metaphysics' with 'c' removed is 'metaphysis'.
'metaphysis' is an anagram of 'SYMPATHISE'.
'to' acts as a link.
(Other definitions for sympathise that I've seen before include "Express fellow feeling" , "commiserate" .)