He’s back from Iceland (4)
I believe the answer is:
alec
'he's' is the definition.
(I've seen this before)
'back from iceland' is the wordplay.
'back' says the letters should be written in reverse.
'from' indicates the answer is hidden within the clue.
'cela' can be found hidden inside 'iceland'.
'cela' reversed gives 'ALEC'.
(Other definitions for alec that I've seen before include "Smart chap" , "Guinness (a smart lad?)" , "A smart . . . . is a know-all in lace" , "Smart boy?" , "Sir - Douglas-Home, former PM" .)