I don't do this crossword but could I relate to the setter? Perhaps DAC or DAC???
As semi detached could be half of
DAC + ha(ve) giving dacha? or DAC(???) + ha(ve)?
I've just googled "DAC crossword compiler" and DAC is a pseudonym of an Independent setter so if this is one of his it will parse as;
I = DAC + ha(ve) = have semi-detached