Condition of being new in service (4)
I believe the answer is:
acne
'condition' is the definition.
(acne is a kind of condition)
'being new in service' is the wordplay.
'being new' becomes 'n'.
'in' indicates putting letters inside.
'service' becomes 'ace' (ace is a kind of service**).
'n' going into 'ace' is 'ACNE'.
'of' acts as a link.
(Other definitions for acne that I've seen before include "Spotty skin condition" , "Skin affliction" , "Skin spots" , "Adolescent skin disease" , "Teenage skin blemish" .)