Unknown soldier transfixed by love guru (4)
I believe the answer is:
yogi
'guru' is the definition.
(thesaurus)
'unknown soldier transfixed by love' is the wordplay.
'unknown' becomes 'y' (algebra).
'soldier' becomes 'gi' (term for US soldier).
'transfixed by' means one lot of letters goes inside another.
'love' becomes 'o' (love means zero in tennis).
'y'+'gi'='ygi'
'ygi' placed around 'o' is 'YOGI'.
(Other definitions for yogi that I've seen before include "Hindu philosopher" , "philosophy student" , "Flexible figure" , "Practitioner of yoga" , "Guru's student" .)