Hermit got troubled by an insect (5,4)
I believe the answer is:
tiger moth
'an insect' is the definition.
(tiger moth is a kind of insect)
'hermit got troubled' is the wordplay.
'troubled' indicates anagramming the letters.
'hermit'+'got'='hermitgot'
'hermitgot' with letters rearranged gives 'TIGER-MOTH'.
'by' is the link.
(Other definitions for tiger moth that I've seen before include "Woolly bear" , "Spotted flyer" , "this one has brightly-coloured wings" , "Plane" , "producer of woolly bears" .)