Dangerous area? Possibly, if men lied (9)
I believe the answer is:
minefield
'dangerous area?' is the definition.
(I've seen this before)
'possibly if men lied' is the wordplay.
'possibly' indicates an anagram.
'if'+'men'+'lied'='ifmenlied'
'ifmenlied' with letters rearranged gives 'MINEFIELD'.
(Other definitions for minefield that I've seen before include "Highly delicate situation (where one must watch one's step!)" , "Dangerous area" , "Sensitive area" , "Danger zone" .)