Heard Moore joins society first - it's a cover up (6)
I believe the answer is:
sheath
'cover up' is the definition.
'sheath' can be an answer for 'cover' (I've seen this before). I'm not sure about the 'up' bit.
'heard moore joins society first it's a' is the wordplay.
I cannot really see how this works, but
'society' could be 's' (common abbreviation in names of organisations) and 's' is found in the answer.
'first' could be 'a' and 'a' is found within the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sheath that I've seen before include "coat" , "Cover protecting" , "Sword covering" , "Cover for a knife" , "Holder for a dagger" .)