‘Unlease a stranger from a kiss’ means to turn a good relationship bad, to turn your lover into a stranger. The song is in the voice of Fish’s alter-ego, the Harlequin, a mischievious and Machiavellian character. Another take on this might be that he unintentionally turns his lover into a stranger by his erratic behaviour.
‘Who hypnotised the guilt in career rhythm trance’. Career rhythm trance refers to the job of a popstar - of Fish, or his alter-ego. He channels his guilt, his feelings of having let people down, into his art, into his songs. You could rewrite it as ‘to come to terms with my guilt through my music’.
There’s a similar idea expressed in these lines in ‘Script For A Jester’s Tear’:
I act the role in classic style of a martyr carved with twisted smile
To bleed the lyric for this song to write the rites to right my wrongs
An epitaph to a broken dream to exorcise this silent scream
I’ve been meaning to sit down and decipher the metaphors in Fish’s Marillion lyrics for a while, but in the end it’s all down to opinion…
Good luck with your project!