Every other beer keeps flier a little tense (9)
I believe the answer is:
alternate
'every other' is the definition.
(synonyms)
'beer keeps flier a little tense' is the wordplay.
'beer' becomes 'ale' (I've seen this before).
'keeps' means one lot of letters goes inside another.
'flier' becomes 'tern' (type of bird).
'little' says to take the initial letters.
The initial letter of 'tense' is 't'.
'tern'+'a'+'t'='ternat'
'ale' placed around 'ternat' is 'ALTERNATE'.
(Other definitions for alternate that I've seen before include "Occur in turn repeatedly" , "Change to first the one, then the other" , "Go in turns" , "Every second one of a series" , "go back and forth" .)