This person turned up and encountered an insect (5)
I believe the answer is:
emmet
'an insect' is the definition.
(emmet is a kind of insect)
'this person turned up and encountered' is the wordplay.
'this person' becomes 'me' (I've seen this in other clues).
'turned up' shows that the letters should be reversed in order.
'and' is a charade indicator (letters next to each other).
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'me' reversed gives 'em'.
'em'+'met'='EMMET'
(Other definitions for emmet that I've seen before include "Ant - to the Cornish, a tourist - met me (anag)" , "one holidaying in Cornwall" , "Irish nationalist, Robert (1778-1803)" , "someone doing the Eden Project?" , "Hill-dweller" .)