Hard work, moving rudder, taking in grey top and yellow top (8)
I believe the answer is:
drudgery
'hard work' is the definition.
(I've seen this before)
'moving rudder taking in grey top and yellow top' is the wordplay.
'moving' indicates anagramming the letters (letters are moved around).
'taking in' means one lot of letters goes inside another.
'top' indicates taking the first letters (in a down clue, the first letter is top).
'and' is a charade indicator (letters next to each other).
'top' indicates taking the first letters (in a down clue, the first letter is top).
The first letter of 'grey' is 'g'.
The initial letter of 'yellow' is 'y'.
'rudder' anagrammed gives 'druder'.
'druder' enclosing 'g' is 'drudger'.
'drudger'+'y'='DRUDGERY'
(Other definitions for drudgery that I've seen before include "chores" , "tedium" , "Boring hard work" , "Hard and tedious work" , "Grinding toil" .)