Absentee boy turned up. In what way? (2-4)
I believe the answer is:
no-show
'absentee' is the definition.
(I've seen this before)
'boy turned up in what way?' is the wordplay.
'boy' becomes 'son' (male child).
'turned up' says the letters should be written in reverse.
'in what way?' becomes 'how' (synonyms).
'son' backwards is 'nos'.
'nos'+'how'='NO-SHOW'
(Other definitions for no-show that I've seen before include "Absentee" , "Person with reservation not turning up" , "Individual neither using nor cancelling a ticket" , "Person who fails to cancel -- who's on (anag)" , "One failing to appear as booked" .)