Fashionable hospital department before comprehensive (2,5)
I believe the answer is:
in depth
'comprehensive' is the definition.
(I've seen this before)
'fashionable hospital department before' is the wordplay.
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'hospital' becomes 'h' (abbreviation for hospital on maps).
'department' becomes 'dept'.
'before' is a charade indicator (letters next to each other).
'h' after 'dept' is 'depth'.
'in'+'depth'='IN-DEPTH'
(Other definitions for in depth that I've seen before include "Penetrating" , "Swimmer so able to touch bottom" , "Detailed sort of investigation" , "comprehensive" , "Thorough" .)