Periodically serve Andrew duck (5)
I believe the answer is:
evade
'duck' is the definition.
(synonyms)
'periodically serve andrew' is the wordplay.
'periodically' means one should take alternating letters (letters must be selected 'every so often').
'serve'+'andrew'='serveandrew'
The alternate letters of 'serveandrew' are 'EVADE'.
(Other definitions for evade that I've seen before include "Artfully dodge" , "Dodge, duck" , "Dodge by cleverness or trickery" , "Slyly escape" , "Sidestep" .)