Tonics sent around should be regular and uniform (10)
I believe the answer is:
consistent
'uniform' is the definition.
(synonyms)
'tonics sent around' is the wordplay.
'around' indicates anagramming the letters.
'tonics'+'sent'='tonicssent'
'tonicssent' with letters rearranged gives 'CONSISTENT'.
'should be regular and' 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 consistent that I've seen before include "Steady" , "true to priniciples" , "stable" , "Free from contradiction" , "uniform" .)