Hypothesis initially dropped by the firm, open to checking (8)
I believe the answer is:
testable
'hypothesis initially dropped by the firm open to checking' is the definition.
I can't judge whether this definition defines the answer.
'hypothesis initially dropped by the firm open to' is the wordplay.
'hypothesis' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'initially dropped' means to remove the first letter.
'by' becomes 'at'.
'the firm' becomes 'stable' (I've seen this before).
'open to' is an insertion indicator (some letters open up to include others).
'at'+'stable'='atstable'
'atstable' with its initial letter taken off is 'tstable'.
'e' going into 'tstable' is 'TESTABLE'.
Can you help me to learn more?
(Other definitions for testable that I've seen before include "Able to be checked" , "(Of a theory) checkable" , "Like pupils taking 12 Across [MOCK EXAMS]" , "open to inspection" .)