Clocks at watchmakers initially go back-and-forth (6)
I believe the answer is:
seesaw
'back-and-forth' is the definition.
(thesaurus)
'clocks at watchmakers initially' is the wordplay.
'clocks' becomes 'sees' (I've seen this before).
'initially' suggests taking the first letters.
The initial letters of 'at watchmakers' is 'aw'.
'sees'+'aw'='SEESAW'
'go' is the link.
(Other definitions for seesaw that I've seen before include "Board balanced on a fulcrum in the playground" , "Fluctuate" , "Up-and-down motion" , "vacillate in policy" , "Plaything with up-and-down movement" .)