LETTER BANK XII

In a letter bank, the letters of one word are used - and repeated as necessary - to spell a longer word or phrase. For example, IMPS is letter bank for MISSISSIPPI. That is, the only letters in MISSISSIPPI are I, M, P, and S - repeated as necessary. In the examples below, the shorter word is clued first.

1. Tango - for one , Moral decline
2. Iconic actor, Eastern US mountain range
3. Malaysian island-city-state / Pavarotti and Sutherland

4)
Nerdy engineers,
When designing _ _ _ _ _ _ _ _ _ (cogged wheels),
Would guard against pen leaks
By wearing _ _ _ _ _ _    _ _ _ _ _ _ _ _ _ _

Answers:

1. DANCE - DECADENCE
2. CHAPLIN - APPALACHIAN 
3. SINGAPORE - OPERA SINGERS 
4. SPROCKETS - POCKET PROTECTORS 

Credits:
The Enigma 
December, 2015
#2-3: NEXT LINGO
#4: ENDGAME