It moves slowly to get up to the centre (8)
I believe the answer is:
tortoise
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'moves slowly to get up to the centre' is the wordplay.
'moves slowly' becomes 'toise' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to get' is an insertion indicator.
'up' becomes 'north' (I've seen this in another clue).
'to the centre' means to look at the middle letters.
The middle letters of 'north' are 'ort'.
'toise' going around 'ort' is 'TORTOISE'.
Can you help me to learn more?
(Other definitions for tortoise that I've seen before include "Slow-moving land reptile" , "one progresses very slowly" , "Shelled reptile" , "Land turtle" , "he's slow to eat lettuce etc" .)