Search island with people in alliance (11)
I believe the answer is:
combination
'alliance' is the definition.
(thesaurus)
'search island with people' is the wordplay.
'search' becomes 'comb' (combing is a kind of searching).
'island' becomes 'i'.
'with' says to put letters next to each other.
'people' becomes 'nation'.
'comb'+'i'+'nation'='COMBINATION'
'in' acts as a link.
(Other definitions for combination that I've seen before include "Mix" , "Items joined together" , "Mixture" , "Amalgamation" , "Union - coalescence" .)