Death's nigh, perhaps - it may be deadly (10)
I believe the answer is:
nightshade
'it may be deadly' is the definition.
The definition suggests a singular noun which matches the answer.
'death's nigh perhaps' is the wordplay.
'perhaps' indicates anagramming the letters.
'deaths'+'nigh'='deathsnigh'
'deathsnigh' is an anagram of 'NIGHTSHADE'.
Can you help me to learn more?
(Other definitions for nightshade that I've seen before include "Poisonous plant" , "Belladonna" , "See 3" , "protection from the moon's brightness?" , "Plant, maybe deadly" .)