The most common and most likely answer to this crossword clue is the 7 letter word SHUTTLE
I've seen this crossword clue in The Guardian
S
H
U
T
T
L
E
More clues leading to the result SHUTTLE
- . . . . ferry close to losing equilibrium initially
- Linking service not trading regularly till end of June
- Dash hurriedly with temperature dropping, dash to and fro
- Regular traveller close to lovely European capitals
- Endeavour, maybe, to go back and forth
- Transport frequently used by weaver?
- Rapid movement between points / a feature of badminton
- Commute from close to the centre of Castlebar
- Movement between points an element in badminton?
- Spacecraft sealed and let loose
Buddy explains!

The straight part
We know that "Linking service" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case linking service = shuttle.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SHUTTLE mean?
SHUTTLE noun- The part of a loom that carries the woof back and forth between the warp threads.
- The sliding thread holder in a sewing machine, which carries the lower thread through a loop of the upper thread, to make a lock stitch.
- A transport service (such as a bus or train) that goes back and forth between two places, sometimes more.
- Such a transport vehicle; a shuttle bus; a space shuttle.
- Any other item that moves repeatedly back and forth between two positions, possibly transporting something else with it between those points (such as, in chemistry, a molecular shuttle).
- A shuttlecock.
- A shutter, as for a channel for molten metal.
- To go back and forth between two places.
- To transport by shuttle or by means of a shuttle service.