If you’re trying to watch the output of an alias, you need to make watch an alias of watch as well.
For example, if you have an alias like say:
alias zfslist='zfs list -o name,volsize,used,avaiable,referenced,compressratio,mountpoint'
And want to watch the output over time as if you ran:
user@host:~/$ watch zfslist
Then you need to set up watch as an alias to watch, as follows.
alias watch='watch '
The space after watch is necessary to get bash to expand subsequent aliases after the first one.