Second rank or front? (4)
I believe the answer is:
brow
'front?' is the definition.
(thesaurus)
'second rank' is the wordplay.
'second' becomes 'b' (B can mean second eg B-side**).
'rank' becomes 'row'.
'b'+'row'='BROW'
'or' acts as a link.
(Other definitions for brow that I've seen before include "Crest" , "Hill part -- head part" , "intellectual level" , "Surprised one can raise this" , "Forehead or hill summit" .)