A boom raises the impulse (7)
I believe the answer is:
upsurge
'a boom' is the definition.
(thesaurus)
'raises the impulse' is the wordplay.
'raises' becomes 'ups' (I've seen this in another clue).
'the impulse' becomes 'urge' ('urge' can be a synonym of 'impulse').
'ups'+'urge'='UPSURGE'
(Other definitions for upsurge that I've seen before include "A sudden rise as in fortunes" , "A sudden rise, as in business" , "Sudden or abrupt strong increase" , "Sudden large increase" , "Hike" .)