Straight transgression on church and bible study (7)
I believe the answer is:
sincere
'straight' is the definition.
(I've seen this in another clue)
'transgression on church and bible study' is the wordplay.
I cannot quite understand how this works, but
'transgression' could be 'sin' (sin is a kind of transgression) and 'sin' is found within the answer.
'on' could be 're' ('on' can be mean 'with reference to') and 're' is found within the answer.
'church' could be 'ce' (abbreviation for Church of England) and 'ce' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sincere that I've seen before include "devout" , "Lacking in deceit" , "Honest, frank" , "Without deceit, genuine" , "natural?" .)