Go past ice, finally, and slip (6)
I believe the answer is:
elapse
'go past' is the definition.
(I've seen this before)
'ice finally and slip' is the wordplay.
'finally' indicates one should take the final letters.
'and' says to put letters next to each other.
'slip' becomes 'lapse' (lapsing is a kind of slipping**).
The last letter of 'ice' is 'e'.
'e'+'lapse'='ELAPSE'
(Other definitions for elapse that I've seen before include "Go past" , "pass in silence" , "Of time, pass by - please" , "Passing" , "Slip away" .)