Repeatedly showing an increase (5)
I believe the answer is:
again
'repeatedly' is the definition.
(I've seen this before)
'an increase' is the wordplay.
'an' becomes 'a'.
'increase' becomes 'gain' (gaining is a kind of increasing).
'a'+'gain'='AGAIN'
'showing' acts as a link.
(Other definitions for again that I've seen before include "Repeatedly" , "Moreover - a second time" , "Here we go ___" , "return" , "One more time, encore" .)