It doesn't normally grow up (4)
I believe the answer is:
root
'grow up' is the definition.
'root' can be an answer for 'grow' (thesaurus). I am unsure of the 'up' bit.
'it doesn't normally' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
The remaining letters 'roo' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for root that I've seen before include "essential nature" , "Solution of equation" , "Derivation" , "Origin; carrot perhaps" , "burrow" .)