1) Ab initio 2) At first 3) At first blush 4) At the beginning 5) At the outset 6) At the start 7) First 8) First of all 9) To begin with 10) To start with Found on https://www.crosswordclues.com/clue/initially
[Adverb] At first, in the beginning. Example: Initially, David turned down the job but then he changed his mind. See also: initial
Found on http://www.bbc.co.uk/skillswise/glossary/