Phlegmatic type, good person originally often in charge (5)
I believe the answer is:
stoic
'phlegmatic type' is the definition.
(I've seen this before)
'good person originally often in charge' is the wordplay.
'good person' becomes 'st' (saint).
'originally' indicates taking the first letters.
'in charge' becomes 'ic' (abbreviation for 'in charge').
The initial letter of 'often' is 'o'.
'st'+'o'+'ic'='STOIC'
(Other definitions for stoic that I've seen before include "Athenian philosopher" , "Resigned" , "One who endures pain with equanimity" , "Long-suffering type; follower of Zeno" , "Uncomplaining in suffering" .)