Solution: The first thing to look at is the example, given on the lefthand side. The word "EXAMPLE" has had its Es and As traded. Looking at the two words below, we see that they are (A) synonyms and (B) start with "A" and "E" respectively. From this, we see the way to solve: find the synonym pairs and swap their initial letters.

The 16 puzzle words form into 8 pairs as follows:
tip - lead
input - enter
ready - arm
owner - head
drive - will
nest - perch
fresh - green
search - comb

Swapping thier initial letters in the given letter string (T -> L, I -> E, etc.), we get:
TIPFLOHGCISHPWCOHALICLDHAWNREA LENGTHOFSECONDSHORTESTWORDPAIR

The second-shortest word pair is READY ARM, which (not counting spaces) gives a total length of EIGHT, the solution to this puzzle.