Obvious need to get across to the treatment centre (5)
I believe the answer is:
overt
'obvious' is the definition.
(similar in meaning)
'across to the treatment centre' is the wordplay.
'across' becomes 'over' (synonyms).
'to' means one lot of letters go next to another.
'centre' means to look at the middle letters.
The central letter of 'treatment' is 't'.
'over'+'t'='OVERT'
'need to get' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for overt that I've seen before include "Openly displayed" , "Done or shown openly" , "Open and undisguised" , "This is not hard to see" , "Clear" .)