Deceitful person going wrong way, boss in terminal situation (8)
I believe the answer is:
railhead
'terminal situation' is the definition.
(as in a train terminal)
'deceitful person going wrong way boss' is the wordplay.
'deceitful person' becomes 'liar'.
'going wrong way' shows that the letters should be reversed in order.
'boss' becomes 'head' ('head' can be a synonym of 'boss').
'liar' reversed gives 'rail'.
'rail'+'head'='RAILHEAD'
'in' acts as a link.
(Other definitions for railhead that I've seen before include "You've reached the end of the line here" , "Terminal of the track" , "End of the train line" , "end of the line - with 26d" .)