GR translation: some collar of love’s nettles now at him

[Mike Jing]

P36.36-P37.7   He will be scrupulous about never telling her. But
there are times when it’s agony not to go to her feet, knowing she
won’t leave Clive, crying you ‘re my last chance . . . if it can’t be
you then there’s no more time. . . . Doesn’t he wish, against all
hope, that he could let the poor, Western-man’s timetable go. . . but
how does a man. . . where does he even begin, at age 33. . . . “But
that’s just it” she’d have laughed, not so much annoyed (she would
have laughed) as tickled by the unreality of the problem—herself too
lost at the manic edge of him, always at engage, so taking, cleaving
her (for more than when jerking off into an Army flannel in the
Persian Gulf was some collar of love’s nettles now at him, at his
cock), too unappeasable for her not to give in to the insanity of, but
too insane really even to think of as any betrayal of Clive. . . .

(for more than when jerking off into an Army flannel in the Persian
Gulf was some collar of love’s nettles now at him, at his cock)

I am having trouble parsing this part in the parentheses.  What is
this all about?