Insect -- chap's holding it up (6)
I believe the answer is:
mantis
'insect' is the definition.
(I know that mantis is a type of dictyopterous insect)
'chap's holding it up' is the wordplay.
'chap's' becomes 'mans' (chap can mean a man).
'holding' means one lot of letters goes inside another.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'it' reversed gives 'ti'.
'mans' going around 'ti' is 'MANTIS'.
(Other definitions for mantis that I've seen before include "Praying ..., long-bodied, large-eyed insect" , "Large-eyed insect, looks as if it's praying" , "Large insect (sometimes praying?)" , "Predatory insect" , "Insect in attitude of prayer" .)