At sea, I toe safe pack-ice, having absolutely no trouble with it (3,1,5,2,4)

'at sea i toe safe' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'pack-ice having absolutely no trouble with it' is the wordplay.
I cannot really understand how this works, but
an anagram of 'ice' is 'iec' which is located in the answer.
'no' could be 'o' (O resembles 0) and 'o' is found in the answer.
'it' could be 'sa' (old-fashioned abbreviation for sex appeal) and 'sa' is found in the answer.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?