Search island shed: nitrogen found inside (7)
I believe the answer is:
manhunt
'search' is the definition.
(manhunt is a kind of search)
'island shed nitrogen found inside' is the wordplay.
'island' becomes 'Man' (the Isle of Man is an example).
'shed' becomes 'hut' (I've seen this in another clue).
'nitrogen' becomes 'N' (N is the chemical symbol for nitrogen).
'found inside' means one lot of letters goes inside another.
'hut' enclosing 'n' is 'hunt'.
'man'+'hunt'='MANHUNT'
(Other definitions for manhunt that I've seen before include "in which one wanted to be found?" , "Organised search for a fugitive" , "Search for criminal" , "Police search operation" , "Pursuit of missing person" .)