Children's author I see in detail, lacking content (4)
I believe the answer is:
dahl
'children's author' is the definition.
(Roald Dahl)
'i see in detail lacking content' is the wordplay.
'i see' becomes 'ah' (exclamation used to indicate understanding).
'in' indicates putting letters inside.
'lacking content' says to hollow out the word (remove centre letters) (the content of the word is emptied out).
'detail' with its centre taken out is 'dl'.
'ah' going inside 'dl' is 'DAHL'.
(Other definitions for dahl that I've seen before include "Roald -, Br. author" , "British author, notably of children's books, d.1990" , "British writer notably of children's books" , "British writer of many children's books, d. 1990" , "Indian dish of legumes and spices" .)