Fertile spot in Samoa's islands (5)
I believe the answer is:
oasis
'fertile spot' is the definition.
(I've seen this before)
'in samoa's islands' is the wordplay.
'in' indicates the answer is hidden within the clue.
'OASIS' can be found hidden inside 'samoas islands'.
(Other definitions for oasis that I've seen before include "Florist's foam" , "Band with Liam and Noel Gallagher" , "Green area in desert" , "Green spot; rock group" , "provides refuge" .)