Routine America oddly unable to follow (5)
I believe the answer is:
usual
'routine' is the definition.
(synonyms)
'america oddly unable to follow' is the wordplay.
'america' becomes 'US' (United States).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'to follow' is a charade indicator (letters next to each other) (some letters go after or follow others).
The alternate letters of 'unable' are 'ual'.
'us'+'ual'='USUAL'
(Other definitions for usual that I've seen before include "Typically done" , "regarding customs?" , "Standard" , "Unexceptional" , "Normal, habitual" .)