Must somehow get the painting back into the bank (7)
I believe the answer is:
stratum
'the bank' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'must somehow get the painting back' is the wordplay.
'somehow' indicates an anagram.
'get' means one lot of letters goes inside another.
'the painting' becomes 'art' (painting is an art).
'back' says the letters should be written backwards.
'art' backwards is 'tra'.
'must' anagrammed gives 'stum'.
'stum' going around 'tra' is 'STRATUM'.
'into' acts as a link.
Can you help me to learn more?
(Other definitions for stratum that I've seen before include "Bed of sedimentary rock" , "stretch of rock" , "Layer (of rock)" , "Social class - level" , "(Geological) layer" .)