Which Order Cards Resolve from Stack - MTG
This is what happens:


Your opponent casts Silverstrike targeting your creature.  
You cast Titanic Growth.  
Titanic Growth resolves, giving your creature +4/+4 until end of turn.  
Silverstrike resolves and destroys your creature.  
Damage happens but there are no creatures to deal damage anymore.


"Until end of turn" just means that the effect of the spell, in this case +4/+4, remains until the end of the turn.  


  405.5. When all players pass in succession, the top (last-added) spell or ability on the stack resolves. If the stack is empty when all players pass, the current step or phase ends and the next begins.  


In this rule you can see that the next step, combat damage, will only happen after the full stack is resolved, including the Silverstrike.