Guards fed up with tips (7)
I believe the answer is:
defends
'guards' is the definition.
(I know this)
'fed up with tips' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'with' is a charade indicator (letters next to each other).
'tips' becomes 'ends' (I've seen this in another clue).
'fed' reversed gives 'def'.
'def'+'ends'='DEFENDS'
(Other definitions for defends that I've seen before include "Protects from attack" , "Supports" .)