Expert tackling new problem one may have to face (4)
I believe the answer is:
acne
'problem one may have to face' is the definition.
I can't tell whether this defines the answer.
'expert tackling new' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'tackling' is an insertion indicator (to tackle is to take possession of).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'ace' placed around 'n' is 'ACNE'.
Can you help me to learn more?
(Other definitions for acne that I've seen before include "Skin problem, mainly of teenagers" , "Skin condition associated with pimples" , "Teenage skin blemish" , "Youthful problem" , "Inflammation of glands in skin" .)