Reasonably clear line to call grass - revealing the presence of some low life? (5,4)
I believe the answer is:
fairy ring
'grass revealing the presence of some low life?' is the definition.
(area of grass said to be used by fairies)
'reasonably clear line to call' is the wordplay.
'reasonably' becomes 'fairly' (synonyms).
'clear' indicates named letters should be taken away.
'line' becomes 'l'.
'to call' becomes 'ring' ('ring' can be a synonym of 'call').
'fairly' with 'l' removed is 'fairy'.
'fairy'+'ring'='FAIRY RING'
(Other definitions for fairy ring that I've seen before include "Dark circle" , "Fungal circle" , "Circular phenomenon due to fungus, associated with imaginary beings" .)