Pat left pathetic Charlie inside, frantic (6)
I believe the answer is:
hectic
'frantic' is the definition.
(I've seen this before)
'pat left pathetic charlie inside' is the wordplay.
'left' is a deletion indicator.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'inside' is an insertion indicator.
'pathetic' with 'pat' taken away is 'hetic'.
'hetic' enclosing 'c' is 'HECTIC'.
(Other definitions for hectic that I've seen before include "Extremely busy - fevered" , "Agitated and rushed" , "Frantically active" , "Marked by intense agitation - fevered" , "Involving feverish activity, flushed" .)