Periodically claim total I earn will get reduced (7)
I believe the answer is:
littler
'reduced' is the definition.
(to reduce is to make littler)
'periodically claim total i earn' is the wordplay.
'periodically' means one should take alternating letters (letters must be selected 'every so often').
'claim'+'total'+'i'+'earn'='claimtotaliearn'
The alternating letters of 'claimtotaliearn' are 'LITTLER'.
'will get' acts as a link.
(Other definitions for littler that I've seen before include "Relatively small" , "Comparatively minor" .)