Hang around, at first, looking on in the extreme rear (6)
I believe the answer is:
loiter
'hang around' is the definition.
(synonyms)
'first looking on in the extreme rear' is the wordplay.
'first' says to take the initial letters.
The initial letters of 'looking on in the extreme rear' is 'LOITER'.
'at' acts as a link.
(Other definitions for loiter that I've seen before include "Hang about idly" , "Hang around, lurk" , "Hang about, with 25 dn perhaps" , "Linger aimlessly" , "Linger - lurk" .)