Thorough girl and boy turning up (8)
I believe the answer is:
detailed
'thorough' is the definition.
(I've seen this in another clue)
'girl and boy turning up' is the wordplay.
'girl' becomes 'delia' ().
'and' is a charade indicator (letters next to each other).
'boy' becomes 'ted' (short for Edward or Theodore).
'turning up' says the letters should be written backwards.
'delia'+'ted'='deliated'
'deliated' in reverse letter order is 'DETAILED'.
(Other definitions for detailed that I've seen before include "Itemized or intricate" , "Elaborate" , "Giving full particulars" , "Meticulous" , "supplying full particulars" .)