Everything is back to front in Holland (3)
I believe the answer is:
all
'everything' is the definition.
(all things)
'back to front in holland' is the wordplay.
'back to front' says the letters should be written in reverse.
'in' says the answer is hidden in the clue.
'lla' is hidden within 'holland'.
'lla' written backwards gives 'ALL'.
'is' acts as a link.
(Other definitions for all that I've seen before include "Fully clad ..." , "'Bless 'em - - ' (song)" , "and 18: 'Sing through -- --' (carol)" , "'... things come to those who wait'" , "See 10 Across" .)