Station with rodent penetrating layers (6)
I believe the answer is:
strata
'layers' is the definition.
(I know this)
'station with rodent penetrating' is the wordplay.
'station with' becomes 'sta' (I have seen 'Short station' mean 'sta' so perhaps 'station' could also mean 'sta'. I am not sure about the 'with' bit.).
'rodent' becomes 'rat' (rat is a kind of rodent).
'penetrating' indicates putting letters inside.
'sta' enclosing 'rat' is 'STRATA'.
Can you help me to learn more?
(Other definitions for strata that I've seen before include "Geological levels" , "Geological layers" , "Layers into which rocks are divided" , "Tiers of thicknesses" , "levels of society" .)