Think I've finally unlocked everything and am satisfied my grid is now correct but the wordplay for 1a is proving annoyingly elusive...
Mark limits strike over lab gear
I've tried to see if the part of the answer "limits" a word for "strike", maybe reversed or "over" or perhaps it contains a word for "limits" without or that "strikes" an "O" but am getting nowhere and tomorrow begins another Listener, so please - someone put me out of my misery:-)