Slowly but surely (4,2,4)
(Other definitions for inch by inch that I've seen before include "Very gradually" , "By small degrees" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">slowly but surely</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for steadily that I've seen before include "with regularity" , "Surely and regularly" , "In regular and balanced way" , "Regularly, without fluctuation" , "Regularly, constantly" .)