Service in French is for surrealist (5)
I believe the answer is:
ernst
'surrealist' is the definition.
(I've seen this before)
'service in french is' is the wordplay.
'service' becomes 'RN' (abbreviation for Royal Navy).
'in' is an insertion indicator.
'french is' becomes 'est' ('is' in the French language).
'rn' inserted within 'est' is 'ERNST'.
'for' is the link.
(Other definitions for ernst that I've seen before include "German-born painter, Max, co-founder of dadaism, d. 1976" , "Max -, twentieth century German Surrealist artist" , "Surrealist; stern (anag.)" , "Young partner" , "Max --, German painter" .)